ECA oxide-resistant connection to a hermetic seal ferrule for an active implantable medical device

ABSTRACT

A hermetically sealed feedthrough assembly for an active implantable medical device having an oxide-resistant electrical attachment for connection to an EMI filter, an EMI filter circuit board, an AIMD circuit board, or AIMD electronics. The oxide-resistant electrical attachment, including an oxide-resistant sputter layer 165 is disposed on the device side surface of the hermetic seal ferrule over which an ECA stripe is provided. The ECA stripe may comprise one of a thermal-setting electrically conductive adhesive, an electrically conductive polymer, an electrically conductive epoxy, an electrically conductive silicone, an electrically conductive polyimides, or an electrically conductive polyimide, such as those manufactured by Ablestick Corporation. The oxide-free electrical attachment between the ECA stripe and the filter or AIMD circuits may comprise one of gold, platinum, palladium, silver, iridium, rhenium, rhodium, tantalum, tungsten, niobium, zirconium, vanadium, and combinations or alloys thereof.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. provisional applicationSer. No. 62/979,600, filed on Feb. 21, 2020 and U.S. provisionalapplication Ser. No. 63/021,858, filed on May 8, 2020.

The present application is also a continuation-in-part of U.S.application Ser. No. 17/077,337, filed on Oct. 22, 2020, now U.S. Pat.No. 11,185,705, which is a continuation of U.S. App. Ser. No.16/854,138, filed on Apr. 21, 2020, now U.S. Pat. No. 10,828,498.

The contents of all the above applications are fully incorporated hereinby these references.

FIELD OF THE INVENTION

The present invention generally relates to hermetic seal subassembliesfor active implantable medical devices (AIMDs). More particularly, thepresent invention relates to an oxide-resistant, low impedance (lowresistance) and very stable electrical connection to an ECA stripedisposed on a hermetic seal ferrule. The oxide-resistant and lowresistance KA stripe provides for connection of EMI filters, EMI filtercircuit boards, AIMD active electronics or circuit boards.

BACKGROUND

Most present day active implantable medical devices (AIMDs) have one ormore electronic circuits enclosed in a hermetically sealed conductivehousing or casing. Common prior art AIMDs, including cardiac pacemakersand implantable defibrillators, have a housing that is made of titanium.Titanium, and two of its alloys, titanium-niobium and titanium-tantalum,are biocompatible and they exhibit physical and mechanical propertiessuperior to many other metals. For example, titanium exhibits excellentcorrosion resistance because, when titanium comes in contact oxygen orwater, instead of corroding, titanium produces an oxide on its surface,which gets stronger over time, which constantly enhances its resilienceagainst corrosive agents. Few substances can breach or even damage thisprotective oxide film, and even if the oxide film is mechanicallyfractured, the oxide film almost immediately regenerates. Hence,titanium is the material of choice for applications requiringbiocompatibility and biostability, such as AIMDs.

For electromagnetic compatibility (EMC) and resistance toelectromagnetic interference (EMI), it is typical that AIMDs compriseone or more filters at or near leadwire ingress or egress into an AIMDhousing. A hermetically sealed feedthrough or a or feedthroughsubassembly is typically located at the point of ingress into the AIMDhousing. This hermetically sealed feedthrough typically comprises ametallic ferrule, such as titanium, and an insulator, such as an aluminaceramic, a glass, or a glass-ceramic. One or more electrical conductorspass through the insulator in non-conductive relationship with theferrule, which are hermetically sealed to the insulator. The insulatoris also hermetically sealed to the ferrule. The AIMD EMI (or MRI)filters divert undesirable EMI signals that are coupled to an implantedlead to the AIMD housing where such signals are harmlessly dissipated asa few milliwatts of heat energy. Thus, dangerous EMI is prevented fromentering into the housing of the AIMD where it may disrupt the properoperation of biological sensing circuits or therapy delivery circuits.The ferrule of the hermetically sealed feedthrough is typically laserwelded into the opening of the housing or casing of the AIMD. The laserwelding process generates a great deal of localized heat, which leads tothickening of the surface titanium oxides, particularly the titaniumoxides on the ferrule of the hermetically sealed feedthrough. This makeselectrical connection of a filter, a filter circuit board, an AIMDactive filter, or an AIMD active circuit board to the ferrule verychallenging. For an EMI or MRI filter to work properly, the electricalconnection of the filter to the ferrule must have a very low equivalentseries resistance (ESR) so that a maximum amount of EMI energy isdissipated (filtered) to the AIMD housing thereby preventing the EMIenergy from entering into the inside of the AIMD housing, where the EMIenergy can cause undesirable, even dangerous life-threatening, devicetherapy delivery issues [a particular concern for cardiac implantableelectronic devices (CIEDs)]. The AIMD housing, which is thermally andelectrically conductive and generally of titanium, provides both an EMIshield and a hermetic seal to the AIMD. High frequency energy, such asthat from microwave ovens, is reflected and absorbed by this titaniumhousing or shield. In addition, EMI filters intercept undesirablesignals that are coupled to or radiated onto AIMD implanted leads (whichact as antennas) and divert such undesirable signals to the titaniumhousing, thereby preventing entry into the AIMD electronics.

Referring once again to titanium and EMI diversion, it is the excellentcorrosion resistance and biocompatibility of titanium that causesconcern regarding the efficacy of EMI filter electrical connections. Aspreviously noted, titanium's excellent corrosion resistance is due tothe formation of a thermodynamically stable, continuous, highlyadherent, and protective surface oxide film. Since titanium metal ishighly reactive and has an extremely high affinity for oxygen, thissurface oxide film is formed spontaneously and instantly when a freshtitanium metal surface is exposed to air and/or moisture. In fact, adamaged titanium oxide film can generally re-heal itself instantaneouslyif even at least traces (that is, a few parts per million) of oxygen orwater are present in the environment. Researchers have proven thatwithin a millisecond of exposure of titanium to air, a 10 nm titaniumoxide layer will be formed on the cut surface of the exposed titaniummetal. This titanium oxide layer will grow to about 100 nm thick withina minute. While a titanium oxide layer on the highly reactive titaniummetal surface imparts good corrosion resistance and provides highbiocompatibility and biostability as noted, such a titanium oxide layercan and does undesirably impact AIMD EMI filter performance. It isfurther noted that, besides affecting EMI filters, the undesirableimpact is even more observable at higher frequency applications, such asswitching applications, coupling applications, and bypass applications.

Prior art addresses oxidation layers on metals, such as a titanium oxidelayer, by cleaning the surface of a metal component, for example, atitanium ferrule or a titanium casing of an AIMD, and then disposing astripe of a thermal-setting conductive adhesive, in other words, anelectrically conductive adhesive (ECA) stripe, atop the “cleaned” metalsurface. The problem with this approach is that (1) the ECA stripe mustbe cured at an elevated temperature of between 200° C. and 300° C.; and(2) the casing must be laser welded to hermetically seal the AIMD.During curing of the ECA stripe, which is conducted in air, the titaniumoxide, which is initially cleaned from the titanium surface of theexemplary ferrule of the feedthrough, almost immediately reforms. Inother words, a titanium oxide layer is now present between the ECAstripe and the cleaned titanium ferrule surface. Similarly, when thecasing of the pulse generator of the AIMD is laser welded, a temperaturerise to the surrounding area results. The laser weld, which is typicallyin close proximity of the ECA stripe, can thereby directly causeadditional titanium oxide formation at the attachment point between theECA stripe and the initially cleaned but subsequently oxidized titaniumpost ECA cure, as elevated temperature exposure of an ECA, such as anepoxy or a polymer, typically allows the release or outgassing of oxygenand/or oxygen-containing constituents or residues that are often presentwithin the ECA material itself. More importantly, this additionalexposure to oxygen or oxygen-containing constituents causes potentiallyharmful thickening of the titanium oxide layer that was previouslycreated during the ECA curing process. Hence, during AIMD manufacturing,the equivalent series resistance (ESR) of the EMI filter can dangerouslyincrease such that EMI filtering is significantly compromised or evenfails. Such potentially unsafe ESR increases are particularly observableat frequencies above 10 MHz. More importantly, and of most concern, isthat the unsafe ESR increases (in other words, EMI capacitor ohmiclosses) are often masked (essentially, totally hidden/indistinguishable)at low frequencies by an EMI filter's dielectric losses. Such masking isparticularly egregious to present day CIEDs, such as pacemakers andimplantable cardioverter-defibrillators, which are considered/labelledMRI conditionally approved, as in an MRI environment, EMI filters divertsubstantial, potentially dangerous, RE current generated in implantedtherapy delivery leads of an AIMD during MRI to the AIMD casing fordissipation. Hence, reliance solely on KA stripe attachment to anoxidizable metal surface, such as a titanium surface, is considered tobe dangerous and of poor practice by the inventors. It is known to oneskilled in the art that electrical connection of AIMD passive EMIfilters to a system ground must be a very low impedance connection,which means that no significant titanium oxides are allowable on anyconnection surface of said system ground.

For AIMDs, there are two types of electronic components. These arepassive components or active components. Passive components do notrequire a source of energy and include capacitors, resistors andinductors. Active components do require an energy source and includemicroelectronic chips, microprocessors, ASIC electronics and the like.For AIMDs, energy sources are typically either a primary or a secondarybattery. However, AIMD energy sources can be coupled energy sourcesthrough either inductive or wireless charging, energy harvesting (forexample, by motion of the myocardium) or even ultrasonic induced energythat is captured.

Accordingly, there is a need for a low resistance and low impedanceelectrical connection having an electrically conductive adhesive stripeand an oxide-resistant layer for attachment of an EMI of activeimplantable medical device.

SUMMARY OF THE INVENTION

The present invention resides in applying an oxide-resistant sputterlayer to device side surface of the ferrule, which has been eithermechanically, chemically or grit blast cleaned of all surface oxides. AnECA stripe, in accordance with the present invention, is disposed overthe oxide-resistant sputter layer to provide a robust electricalattachment pad or stripe for low impedance, low resistance and verystable electrical connection to EMI filters, such as feedthroughcapacitors, internally grounded feedthrough capacitors, MLCC filtercircuit boards, X2Y attenuators, flat-thru capacitors, internalelectronic components, or AMID active circuit boards.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a wire-formed diagram of a generic human body showing a numberof exemplary implantable medical devices;

FIG. 2 is a side view of a prior art cardiac pacemaker;

FIG. 2A is a sectional view of the prior art pacemaker of FIG. 2 ;

FIG. 2B illustrates how an EMI filter can reflect and divert EMI energyfrom entering the pacemaker of FIG. 2A;

FIG. 2C is a sectional view taken from FIG. 2B, illustrating how afeedthrough capacitor works to reflect and divert EMI;

FIG. 3 is a perspective partial cutaway view of a unipolar capacitor;

FIG. 4 is a side sectional view of a similar unipolar capacitor of FIG.3 now mounted to a hermetic feedthrough for an active implantablemedical device;

FIG. 5 is an electrical schematic representation of the unipolarfiltered feedthrough assembly previously illustrated in FIG. 4 ;

FIG. 6 is generally taken along lines 6-6 from FIG. 3 and is an explodedperspective view of the electrode layer stack up;

FIG. 6A is a sectional view similar to FIG. 6 showing the undesirableformation of an oxide layer;

FIG. 6B is the electrical schematic of the oxidized filter of FIG. 6A;

FIG. 6C is an electrical schematic diagram showing how a proper filterworks to divert high frequency EMI to the cardiac implantable electronicdevices (CIEDs) housing, including the family of cardiac pacemakers,implantable defibrillators, implantable loop recorders and the like;

FIG. 6D illustrates an undesirable graph of EMI filter ESR versusfrequency that is heavily oxidized;

FIG. 6E shows an ESR versus frequency curve for another EMI filter thatis attached to a heavily oxidized titanium connection;

FIG. 6F shows the ESR curve versus frequency for a highly oxidizedfilter connection;

FIG. 7 is a perspective view of a quadpolar feedthrough capacitor andhermetic terminal assembly;

FIG. 8 is a sectional view of the feedthrough and hermetic terminalassembly of FIG. 7 taken along lines 8-8, illustrating ground connectionof the EMI filter to an oxide-resistant ferrule hermetic seal goldbraze;

FIG. 9 is an electrical schematic representation of the quadpolarfiltered feedthrough capacitor that has an oxide-free connection, aspreviously illustrated in FIGS. 7 and 8 ;

FIG. 10 is an exploded perspective view of the electrode layer stack upof the structure of FIGS. 7 and 8 ;

FIG. 11 is an ESR curve versus frequency for the quadpolar filter ofFIG. 9 , illustrating greatly reduced ESR;

FIG. 12 is an ESR curve from a solar manufacturing lot. Hundreds ofparts like these overlay FIGS. 11 and 12 like fingerprints.

FIG. 13A illustrates an exploded perspective view of an internallygrounded prior art feedthrough capacitor;

FIG. 13B illustrates the structure of FIG. 13A where now the capacitoris formed as a monolithic structure;

FIG. 13C illustrates the structure of FIG. 13B fully assembled into afeedthrough filtered hermetic terminal;

FIG. 13D is the electrical schematic for the feedthrough filteredhermetic terminal previously described in FIGS. 13A, 13B and 13C;

FIG. 14 illustrates a prior art monolithic ceramic capacitor (MLCC),which is also known in the art as a multilayer ceramic capacitor;

FIG. 15 is a sectional view from the MLCC chip capacitor of FIG. 14showing its internal electrode plates;

FIG. 15A is a top sectional view from the MLCC chip capacitor showingits left-hand active electrode plates;

FIG. 15B is a similar sectional view to FIG. 15A, except in this case,showing the right-hand connected active electrode plates;

FIG. 16 illustrates a prior application of an MLCC chip capacitorsattached to hermetic seal subassembly of an active implantable medicaldevice;

FIG. 17 illustrates a cross-sectional view of a unipolar unfilteredhermetic seal;

FIG. 18 illustrates application of an MLCC chip capacitors attacheddirectly to an oxidized ferrule of an AIMD;

FIG. 18A illustrates a cross-section of the MLCC chip capacitor of FIG.18 , illustrating the elements that give rise to undesirable seriesresistance;

FIG. 18B gives the equations for capacitive reactance and thecapacitor's impedance of FIG. 18 ;

FIG. 18C is the electrical schematic of the capacitor of FIG. 18 showingthe undesirable series resistance that forms from the undesirable seriesresistance that forms from titanium oxides;

FIG. 19 illustrates a prior art flat-thru capacitor;

FIG. 20 is a multiple sectional view of the electrode plate stack-up ofthe structure of FIG. 19 ;

FIG. 21 illustrates a three-terminal capacitor that is also known in theindustry as X2Y attenuator;

FIG. 22 illustrates a three-terminal capacitor that is also known in theindustry as X2Y attenuator;

FIG. 22A illustrates an electrical schematic of the three-terminalcapacitors of FIGS. 21 and 22 ;

FIG. 23 is a perspective view of a prior art MLCC filter circuit boardattached to the ferrule for an AIMD;

FIG. 23A is taken from section 23A-23A from FIG. 23 ;

FIG. 23B is taken from section 23B-23B from FIG. 23 illustrating acircuit board and internal ground plate;

FIG. 23C is taken from section 23C-23C from FIG. 23 illustrating anoxide-resistant circuit board ground pin;

FIG. 23D illustrates that the ground pin of FIG. 23C can be replaced bya spatially aligned ground via over the hermetic seal to ferrule goldbraze;

FIG. 23E illustrates that the circuit board of FIG. 23 may have an edgemetallization that is attached to a metal addition, which is laserwelded or gold brazed to the AIMD ferrule;

FIG. 23F illustrates that the FIG. 23 circuit board can have a groundedge metallization that is connected to a gold pocket-pad, which isformed into a recess in the AIMD ferrule;

FIG. 23G illustrates that circuit board may have an edge groundmetallization that is conductively coupled to an oxide-resistant groundpin described in FIG. 23C;

FIG. 23H is similar to FIG. 23G, except that the ground via hole isspatially aligned over a gold pocket-pad formed in a ferrule recess;

FIG. 23I is the schematic diagram for the oxide-resistant filterattachments previously described in FIG. 23 and FIGS. 23A through 23H;

FIG. 24 illustrates the circuit board of FIG. 23 having a ground edgemetallization, which is undesirably connected to an oxidized AIMDferrule (poor practice);

FIG. 24A is taken from section 24A-24A from FIG. 24 and illustrates thedirect electrical connection to the oxidized ferrule;

FIG. 24B illustrates undesirable oxidize build up over time andtemperature;

FIG. 24C illustrates a highly oxidized ground connection that occursafter laser welding of the ferrule and the opening in the AIMD titaniumhousing;

FIG. 24D is the electrical schematic of the oxide connected filter ofFIG. 24 showing the undesirable R_(OXIDE) in series with the filtercapacitor;

FIG. 25 illustrates an inline feedthrough capacitor that is grounded toan ECA stripe and an oxide-resistant sputter layer in accordance withthe present invention;

FIG. 25A is taken from section 25A-25A from FIG. 25 illustrating theoxide-free connection to the ferrule;

FIG. 26 illustrates an MLCC filtered circuit board with groundattachments to a ferrule ECA stripe and an oxide-resistant sputterlayer;

FIG. 26A is taken from section 26A-26A from FIG. 26 showing theoxide-resistant connection;

FIG. 27 is taken from section 27-27 from FIG. 26 showing the top view ofthe circuit board;

FIG. 28 is taken from section 28-28 from FIG. 26 showing at least onecircuit board ground plate;

FIG. 29 is a sectional view taken from section 29-29 from FIG. 26through the center line of circuit board ground vias;

FIG. 30 is taken from section 30-30 from FIG. 26 showing a sectionalview through the active pins;

FIG. 31 illustrates an alternative method of oxide resistive attachmentof the circuit board of FIG. 26 to an ECA stripe;

FIG. 32 is similar to FIG. 31 showing an alternative attachment using acircuit board via hole;

FIG. 33 is a pictorial view of a prior art reverse geometry MLCC chipcapacitor;

FIG. 34 is a sectional view taken from section 34-34 from FIG. 33 ;

FIG. 35 is a sectional view illustrating the reverse geometry MLCC chipcapacitor attached to an ECA stripe of the present invention;

FIG. 36 illustrates the electrical schematic diagram of the filtercapacitor reverse geometry MLCC chip capacitor of FIG. 33 ;

FIG. 37 illustrates a prior art quadpolar flat-thru filter capacitor;

FIG. 38 are internal section taken from section 38-38 from FIG. 37showing the flat-thru active and ground electrode plates;

FIG. 39 is a sectional view of the flat-thru capacitor of FIG. 37 with aground attachment to the ECA stripe of the present invention;

FIG. 39A illustrates the flat-thru capacitor of FIG. 37 mounted in atombstone position to ECA stripes disposed on a hermetic seal ferrule;

FIG. 39B illustrates the schematic of the flat-thru filter capacitor ofFIGS. 37 and 39A;

FIG. 40 is a pictorial view of a prior art X2Y attenuator;

FIG. 40A is an exploded section showing the active electrode plates ofthe X2Y attenuator of FIG. 40 ;

FIG. 40B is an exploded view showing the ground electrode plates of theX2Y attenuator of FIG. 40 ;

FIG. 40C is an exploded view showing how the ground and active electrodeplates are interleaved for the X2Y attenuator of FIG. 40 ;

FIG. 40D illustrates the X2Y attenuator of FIG. 40 with a groundconnection to the ECA stripe of the present invention;

FIG. 40E illustrates the schematic diagram for the X2Y attenuator ofFIG. 40D;

FIG. 41 illustrates internally grounded feedthrough capacitor attachedto an ECSA stripe on a ferrule peninsula;

FIG. 42 is similar to FIG. 41 wherein, the electrical connection to theECA stripe is accomplished by anisotropic conductive film;

FIG. 43 is a table and listing of all the patents that are hereinincorporated fully by reference.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates various types of active implantable and externalmedical devices 100 that are currently in use. FIG. 1 is a wire formeddiagram of a generic human body showing a number of implanted medicaldevices. 100A is a family of external and implantable hearing deviceswhich can include the group of hearing aids, cochlear implants,piezoelectric sound bridge transducers and the like. 1008 includes anentire variety of neurostimulators and brain stimulators.Neurostimulators are used to stimulate the Vagus nerve, for example, totreat epilepsy, obesity and depression. Brain stimulators are similar toa pacemaker-like device and include electrodes implanted deep into thebrain for sensing the onset of a seizure and also providing electricalstimulation to brain tissue to prevent the seizure from actuallyhappening. The leadwires that come from a deep brain stimulator areoften placed using real time imaging. Most commonly such leadwires areplaced during real time MRI. 100C shows a cardiac pacemaker, which iswell-known in the art and may have endocardial or epicardial leads.Implantable pacemakers may also be leadless. The family of cardiacpacemakers 100C includes the cardiac resynchronization therapy devices(CRT-P and CRT-D) and leadless pacemakers. CRT-P devices are unique inthat they pace both the right and left ventricles of the heart to helpthem contract at the same time to help the heart pump more efficiently.A CRT-D device is a special device for heart failure patients who arealso at high risk for sudden cardiac death. While functioning like anormal pacemaker to treat slow heart rhythms and also delivering smallelectrical impulses to the left and right ventricles to help themcontract at the same time, the CRT-D device is also capable ofdelivering shock to the heart to treat dangerously fast heart rhythmsthat can lead to sudden death. The 100C device family also includes alltypes of implantable loop recorders or biologic monitors, such ascardiac monitors. 100D includes the family of left ventricular assistdevices (LVAD's) and artificial hearts. 100E includes an entire familyof drug pumps, which can be used for dispensing of insulin, chemotherapydrugs, pain medications and the like. Insulin pumps are evolving frompassive devices to ones that have sensors and closed loop systems. Thatis, real time monitoring of blood sugar levels will occur. These devicestend to be more sensitive to EMI than passive pumps that have no sensecircuitry or externally implanted leadwires. 100F includes a variety ofexternal or implantable bone growth stimulators for rapid healing offractures. 100G includes urinary incontinence devices. 100H includes thefamily of pain relief spinal cord stimulators and anti-tremorstimulators. 100H also includes an entire family of other types ofneurostimulators used to block pain. 100I includes a family ofimplantable cardioverter defibrillator (ICD) devices and also includesthe family of congestive heart failure devices (CHF). This is also knownin the art as cardiac resynchronization therapy devices, otherwise knownas CRT devices. 100J illustrates an externally worn pack. This packcould be an external insulin pump, an external drug pump, an externalneurostimulator, a Holter monitor with skin electrodes or even aventricular assist device power pack. Referring once again to element100C, the cardiac pacemaker could also be any type of biologicmonitoring and/or data recording device. This would include looprecorders or the like. Referring once again to FIG. 1, 100I is describedas an implantable defibrillator. It should be noted that these could bedefibrillators with either endocardial or epicardial leads. This alsoincludes a new family of subcutaneous defibrillators.

FIG. 2 illustrates a side cutaway view of a prior art cardiac pacemaker100C. The pacemaker electronic circuits are housed in a hermeticallysealed and conductive electromagnetic shield 102 (typically titanium).There is a header block assembly 104 generally made of thermal-settingnon-conductive plastic, such as Tecothane™. This header block assembly104 houses one or more connector assemblies generally in accordance withISO Standards IS-1, IS-2, or more modern standards, such as IS4 or DF4.The header block connector port assemblies are shown as 106 and 106′.Implantable leadwires 110, 110′ have proximal plugs 108, 108′ and aredesigned to insert into and mate with the header block connectorcavities 106 and 106′, or, alternatively, directly into the pulsegenerator itself for devices that do not have header block assemblies.

Referring once again to FIG. 2 , one can see an active electronics AIMDcircuit board 126. Active circuit boards require a source of electricalenergy, energy storage, power, and combinations thereof. The electricalenergy source comprises a primary battery, a secondary battery, or both;the energy storage source comprises an energy storage capacitor, and thepower source comprises an electrical energy system, a power system, orboth. Active electronics include at least one microelectronic ormicrochip component, for example, but not limited to, anapplication-specific integrated circuit (ASIC) chip or an integratedcircuit (IC) chip. As will be further discussed, a passive electronicselectromagnetic interference (EMI) filter chip may alternatively bedisposed in the location of the feedthrough capacitor 124.

As used herein, the term “lead” refers to an implantable lead containinga lead body and one or more internal lead conductors. A “lead conductor”refers to the conductor that is inside of an implanted lead body. Theterm “leadwire” or “lead wire” refers to wiring that is either inside ofthe active implantable medical device (AIMD) housing or inside of theAIMD header block assembly or both. Furthermore, as used herein, ingeneral, the terms lead, leadwire and pin are all used interchangeably.Importantly, they are all electrical conductors. This is why, in thebroad sense of the term, lead, leadwire or pin can all be usedinterchangeably since they are all conductors. The term “conductivepathway” can also be used to be synonymous with lead conductor, lead,leadwire or pin or even a circuit trace. As described herein, compositeconductive sintered paste filled vias passing through an insulator innonconductive relation with a ferrule electrically acts the same asleadwire, lead wire, or pin. These sintered paste filled vias may alsoincorporate co-fired solid leadwires. As used herein, the term pastegenerally refers to pastes, inks, gels, paints, cermets, and other suchmetal and/or metal/ceramic sinterable material combinations that can beflowable, injectable, pressed, pulled, pushed or otherwise movable intoan orifice or via. Post-sintering, the solvents and binders are bakedout and, after sintering, the paste becomes a densified solid withmonolithic structure. Additionally, AIMD, as defined herein, includeselectronic circuits disposed within the human body that have a primaryor secondary battery, or have an alternative energy source, such asenergy induced by motion, thermal or chemical effects or throughexternal induction. As used herein, the term “header block” is thebiocompatible material that attaches between the AIMD housing and thelead. The term “header block connector assembly” refers to the headerblock including the connector ports for the leads and the wiringconnecting the lead connector ports to the hermetic terminalsubassemblies which allow electrical connections to hermetically passinside the device housing. It is also understood by those skilled in theart that the present invention can be applicable to active implantablemedical devices that do not have a header block or header blockconnector assemblies such as cochlear or retinal implants.

FIG. 2A shows an exemplary sectional view of the AIMD previouslydisclosed in FIG. 2 . In this case, MLCC chip capacitor 194, 194′ filtercomponents are undesirably located on the AIMD circuit board 126, whichis disposed at a distance from the hermetic seal insulator 120 insidethe hermetically sealed housing 102 of the AIMD. In this case, radiatedEMI directly penetrates through the insulator 120 into the interior ofthe AIMD housing 102. In addition, conducted EMI, which is coupled toimplanted leads by induction or antenna action, can enter the AIMDhousing by way of its leadwires. FIG. 2A is thus a representation ofpoor practice as the EMI is allowed to enter inside of the AIMD housing102 before the EMI is filtered by the MLCC chip capacitor 194, 194′ ofother filter components. This can cause the EMI to reradiate on theinside of the AIMD housing, as shown by arrows 103. At high frequencies,this unfiltered EMI can dangerously couple to AIMD sensitive circuits,such as pacemaker sense circuits. Such unfiltered EMI can thereby causemalfunction of the AIMD. In the case of cardiac implantable electronicdevices (CIED) such as an implantable defibrillator or pacemaker, thisEMI interaction can dangerous, even life-threatening.

FIG. 2B is similar to FIG. 2A, except now a feedthrough EMI filtercapacitor 124 is disposed adjacent to the hermetic seal insulator 120.The internal electrode plates, particularly the ground electrode platesof the feedthrough EMI filter capacitor 124, reflect radiated EMI suchthat it cannot enter inside the AIMD housing 102. At the same time, thefilter capacitor diverts conducted EMI, which is dissipated harmlesslyto the AIMD housing 102.

FIG. 2C is taken from section 2C-2C of FIG. 2B illustrating the internalelectrode plates of the feedthrough EMI filter capacitor 124 and itsconnection to the AIMD housing 102, which is system ground. As definedherein, system ground is the housing 102 of an AIMD, which can alsooptionally include a metallic electrically conductive feedthroughferrule 122 hermetically sealed to an insulator 120 of the feedthrough,the ferrule being mechanically and electrically attached to an openingin the AIMD housing by processes, such as, but not limited to, laserwelding or brazing. Alternatively, the ferrule may be formed as acontiguous extension of the AIMD housing.

As used herein, the acronym AIMD stands for active implantable medicaldevices. A family of AIMDs is described in FIG. 1 . As defined herein,active components, such as an active implantable medical device or anactive electronic circuit board, require a source of power or energy,such as a primary or a secondary battery. There are other sources ofenergy involving wireless energy transfer, converting ultrasonic wavesor even energy harvesting derived from biomechanical motions of humanorgans, such as cardiac motion, blood flow, breathing and the like,which collects and stores electric power or energy for later use.Passive AIMD electronic components or passive AIMD circuit boards do notrequire a source of power or energy and consist of passive components,including capacitive, inductive, and resistive elements. Also, asdefined herein are CRT-P and CRT-D devices. These are cardiacresynchronization pacemakers and cardiac resynchronizationdefibrillators. They are different than prior pacemakers anddefibrillators, in that they have a third wire system routed outside theleft ventricle and are thereby able to completely resynchronize theheart.

FIG. 3 illustrates an isometric cut away view of a unipolar feedthroughcapacitor. Shown are active electrode plates 134 and ground electrodeplates 136 both disposed within a capacitor dielectric 154. There is afeedthrough hole (passageway), including metallization 130. There isalso an outside diameter metallization 132.

FIG. 4 illustrates a cross-sectional view of the unipolar capacitor ofFIG. 3 . The unipolar capacitor is mounted to a ferrule 122 of ahermetically sealed feedthrough 116 for an active implantable medicaldevice (AIMD). As shown, the ferrule 122 is configured to be laserwelded 128 into an opening of an AIMD housing previously illustrated inFIG. 2 as element 102. The AIMD housing generally comprises titanium,but can comprise other biocompatible electrically conductive materials,and forms an overall electromagnetic shield to help protect AIMDelectronics from electromagnetic interference (EMI) emitters, such ascell phones and the like. Accordingly, FIG. 4 shows a ground symbol 144indicating that EMI signals, which may couple to the body side of thelead 118, can be decoupled or diverted through the feedthrough capacitor124 to the equipotential electromagnetic shield (the housing of theAIMD). When high frequency EMI signals are diverted from lead 118 to theAIMD housing 102, the EMI signals circulate around the electromagneticshield (the housing) and are converted into meaningless heat (just a fewmilli or microwatts).

Referring once again to FIG. 4 , one will see an electrical connectionmaterial 148 directly connected to the ferrule 122. Typically, theferrule 122 would comprise titanium, which forms oxides. In fact, it isthe oxides of titanium that make it biocompatible. However, these oxidesare very resistive or semi-conductive. It was not known at the time theprior art filters of FIG. 4 were being built that filter performancecould seriously degrade over time due to titanium oxides. Referring onceagain to FIG. 4 , one can see the traditional circuit ground system,labeled system ground 144. As used herein, system ground, represented bythe ground symbol illustrated by FIG. 4 as element 144, can be connectedeither directly to the AIMD housing 102 or to the ferrule 122. Asdefined herein, the schematic ground symbols used throughout the presentpatent drawings represent EMI filter system ground 144. At both low andhigh frequencies, housing 102 and ferrule 122 are at system groundpotential as a result of the continuous laser weld 128 that mechanicallyand electrically joins them together.

FIG. 5 illustrates the schematic diagram for the feedthrough capacitorof FIGS. 3 and 4 , showing that the feedthrough capacitor is athree-terminal device capable of significant high frequency attenuationalong the length of the leadwire extending to the body fluid side leadend 118 and to the device side lead end 118′. Accordingly, the bodyfluid side lead end 118 is a first terminal, the device side lead end118′ is a second terminal, and the system ground 144, which is the AIMDhousing 102, is the third terminal, to which undesirable EMI isdiverted. It is known to one skilled in the art that three-terminalfeedthrough capacitors have very little to no parasitic seriesinductance and are therefore very broadband low pass filters. This meansthat low frequency signals, such as therapeutic pacing pulses orbiologic signals, pass through the body fluid side of the lead 118 tothe device side of the lead 118′ without degradation or attenuation.However, at high frequencies, the capacitive reactance drops to a verylow number and desirably, high frequency signals are selectively shortedout from the lead conductor 118, 118′ to the ferrule 122 and, in turn,to the conductive housing 102. Referring once again to FIG. 5 , one cansee the resistance 164 between the filter capacitor and the systemground (144) symbol. This resistance 164 is highly undesirable andresults from thickening of oxides on the surface of the titanium betweenthe electrical connection 148 of FIG. 4 and the titanium ferrule 122.

FIG. 6 is an exploded view of the unipolar feedthrough filter capacitorof FIG. 3 showing that the feedthrough filter capacitor comprises (fromthe top down): one or more ceramic cover plates 154; active electrodeplates 134 interleaved with ground electrode plates 136; and another setof one or more cover sheets 154. In ceramic engineering, the ceramicdielectrics would typically be of BX or X7R having a dielectric constantof approximately 2000 or higher. It is appreciated that NP0, which isgenerally a low k dielectric with a dielectric constant below 200, canalso be used, which is taught in U.S. Pat. No. 8,855,768, the contentsof which are incorporated fully herein by this reference.

FIG. 6A shows that the feedthrough capacitor ground termination 132 ofFIG. 3 has been electrically connected using and electrical connectionmaterial 143 directly to ferrule 122. Even if one mechanically orchemically cleans the ferrule of all oxides before the electricalconnection is made, a surface oxide 164 can reform between theelectrical connection material 143 and the ferrule 122. The electricalconnection material typically used in this case is a thermal-settingconductive adhesive, such as a conductive polyimide, a conductivepolymer or a conductive epoxy. The ferrule 122 is typically laser welded128 in an opening of the AIMD housing 102. As previously indicated,laser welding creates a substantial amount of localized heat, which canfurther accelerate oxide formation. Even if the inside environment ofthe AIMD housing has been evacuated and backfilled with an inert gas,oxygen can be released from, for example, the thermal-setting conductiveadhesive (electrical connection material 143) as the adhesive is heatedduring the laser welding process. The formation of this surface oxide164 is very detrimental to filter performance, shown as R_(OXIDE) inFIG. 6B.

FIG. 6C is a schematic diagram indicating how high frequency EMIentering from a body fluid side (terminal 1) is diverted through afeedthrough capacitor or filter capacitor C. For the filter capacitor towork properly, its parasitic resistance R_(OXIDE) must be minimized. Ifthe resistance value becomes too large, then the filter performance isseriously compromised. Ideally, high frequency EMI is diverted to systemground (terminal 3) as indicated. However, if resistance due to oxidesform, then filter performance is degraded, and a significant amount ofhigh frequency EMI enters into the device at terminal 2. When R and Lare minimized, then the capacitive reactance X_(C) will approximately beequal to the impedance Z, as indicated in the equation of FIG. 6C.

FIGS. 60 and 6E are graphs of the equivalent series resistance (ESR) offeedthrough capacitors, as previously illustrated in FIG. 6A. What isalarming is that the expected U-shaped ESR curve of these particularfeedthrough capacitors are not present. Even more alarming are the highvalues of ESR for these two capacitors at 100 MHz (1.49 ohms and 1.48ohms). It is noted that ESR sweeps identified five discrepant oxidizedparts from a lot of 1000 prototype filtered feedthrough parts, and thatthis lot of filtered feedthrough parts were built with a thermal-settingconductive adhesive directly connecting the capacitor ground termination132 of the filter capacitor and the ferrule 122 of the feedthrough. Thetwo parts illustrated in FIGS. 60 and 6E are two of the five thatexhibited a high ESR.

FIG. 6F illustrates an ESR versus frequency curve of the most oxidizedpart out of the five parts that had failed in the 1000 piecequalification test lot. In this case, the ESR at 100 MHz is 3.85 ohms.Referring back to FIG. 6C, the capacitive reactance at 100 MHz for atypical 2000 picofarad filter capacitor is 0.796 ohms. One can see thatwhen a surface oxide causes an increased resistance in series with afilter capacitor from less than one ohm to 3.85 ohms the filterperformance of that particular filter capacitor seriously anddangerously degrades.

FIG. 7 illustrates a quadpolar feedthrough capacitor and hermeticterminal subassembly 116 comprising four leadwires 118 a-118 d and fourfeedthrough holes (quadpolar). The hermetic terminal is a metallicferrule 122 generally of titanium, which is ready for laser welding 128into the AIMD housing 102 (not shown).

Referring once again to FIG. 7 , illustrated is a prior art embodimentof an oxide-resistant connection from the capacitor ground metallizationusing electrical connection material 148. In this case, the electricalconnection is not made directly to ferrule 122. This is best understoodby looking at FIG. 8 , which is a cross-sectional view taken fromsection 8-8 of FIG. 7 . FIG. 8 illustrates that the electricalconnection material 148 connecting the capacitor ground termination 132and the ferrule is at least partially contacting the gold braze 140 thathermetically seals the insulator 120 and the ferrule 122. An electricalconnection to an oxide-resistant material, which includes noble metals,for example, a gold braze as shown, provides a very low resistanceconnection that is essentially free of oxides. Connection to the goldbraze of the hermetic seal is further described in U.S. Pat. No.6,765,779, the contents of which are herein incorporated fully by thisreference.

FIG. 8 is a prior art sectional view taken generally from section 8-8from FIG. 7 . The hermetic terminal subassembly leadwires 118 a-d passthrough the hermetic terminal subassembly insulator 120 innon-conductive relationship and also pass through the feedthroughcapacitor 124, wherein the active electrode plates 134 are electricallyconnected 146 to the hermetic terminal subassembly leadwire 118 andwherein the feedthrough capacitor ground electrode plates 136 areelectrically connected 148 to the hermetic terminal subassembly ferrule122 and the gold braze 140.

Referring once again to FIGS. 7 and 8 , in each case it is seen that thehermetic terminal subassembly leadwires 118 a-d pass all the way throughthe entire structure, namely, the hermetic terminal subassembly 116 andthe feedthrough capacitor 124. In general, these hermetic terminalsubassembly leadwires 118 a-d are electrically and mechanicallycontinuous (single material) and pass through from the body fluid sideto the inside of the device 100 housing 102. Because the hermeticterminal subassembly leadwires 118 a-d pass through from the body fluidside to the inside of the device housing by way of header blockconnector assembly 104 or the like, it is very important that thesehermetic terminal subassembly leadwire 118 materials be biocompatible,biostable and non-toxic. Generally, in the prior art, these hermeticterminal subassembly leadwires are constructed of platinum orplatinum-iridium, palladium or palladium-iridium, niobium or the like.Platinum-iridium is an ideal choice because it is biocompatible,non-toxic and is also mechanically very strong. The iridium is added toenhance material ductility and to enable the hermetic terminalsubassembly leadwire to sustain bending stresses. Referring once againto FIGS. 7 and 8 , it is noted that by connecting the capacitor groundtermination 132 to gold braze 140, the outside diameter of thefeedthrough capacitor is thereby constrained, which can make thefeedthrough capacitor volumetrically inefficient.

FIG. 9 illustrates the schematic of the quad polar hermetic terminal ofFIG. 7 . The schematic shows the feedthrough capacitors grounded tosystem ground without series inductance or resistance. The reasoninductance is absent is because feedthrough capacitors are unique inthat they are three-terminal devices that do not have series inductance.More importantly, the reason that the resistance is absent is becausethe ESR of the feedthrough capacitor is so low because the capacitorground is electrically connected to (directly contacts) the hermeticseal insulator to ferrule gold braze, as illustrated in FIG. 8 ; thus,the resistance can be ignored. In other words, FIG. 9 illustrates thatthe feedthrough capacitor of FIGS. 7 and 8 , exhibits nearly idealfilter performance.

FIG. 10 is an exploded view of the quadpolar capacitor 132 of FIG. 7 .In the exploded view, shown are four active electrode plates 134 and oneground plate 136. The overlap of the active electrode 134 with theground electrode 136 determines the effective capacitance area. Thegreater this overlap area, the higher the capacitance of the feedthroughcapacitor. One can also say that this quadpolar capacitor is amultilayer structure. In FIG. 10 , there are two active and two groundplates shown. Increasing the number of active and ground plates has theeffect of increasing the capacitor's effective capacitance area. It isappreciated that as many as 400 or more ground and active layers can beused.

FIGS. 11 and 12 are ESR versus frequency curves for ESR sweeps of thefilter capacitor of FIGS. 7 and 8 , wherein the electrical connection ofthe filter capacitor to the ferrule is made directly to the gold brazehermetically sealing the insulator and the ferrule of the hermeticterminal. In this case, the ESR at 100 MHz is 0.467 ohms and 0.423 ohms.More importantly, the curves of FIGS. 11 and 12 exhibit the expectedclassic capacitor U-shaped ESR curve. A U-shaped ESR curve is “thefingerprint” for a filter capacitor and each curve should overlay oneanother. The reason the ESR increases at low frequency is due to thenormal behavior of the capacitor's dielectric loss tangent. At higherfrequencies, above 10 MHz, the dielectric loss tangent starts todiminish and the ESR curve is dominated by ohmic loss. The U-shapedcurve at high frequencies, such as 500 MHz, is an artifact of atwo-terminal measurement for ESR. The increase in ESR at 500 MHz is dueto skin effect. The most important performance parameter of an EMIfilter is the measurement of insertion loss. Insertion loss is measuredon a spectrum analyzer at swept frequencies. The insertion loss testsindicate that the filters of FIGS. 11 and 12 have ideal insertion lossin decibels (dB) of 28.82 dB (ESR 0.467 ohms) and 29.08 dB (ESR 0.422ohms). One is reminded that insertion loss is a decibel scale, which islogarithmic. A drop in insertion loss of 6 dB will degrade filterperformance by half. For the heavily oxidized filters of FIGS. 6D, 6Eand 6F, insertion loss severely degrades. Even a drop of 3 dB is a stilla significant drop in filter performance. With a 100 MHz ESR of 1.48ohms, the insertion loss is 23.95 dB. For an ESR of 1.49 ohms at 100MHz, the insertion loss is 23.91 dB and for the worst part out of thistest population that had an ESR of 3.86 ohms at 100 MHz, insertion lossdrops to 17.3 dB. Drops in insertion loss like this means that filterperformance is very badly degraded, meaning that filter performance iscompromised creating a situation that can be very dangerous or evenlife-threatening for an CIED patient. A comparison of filter capacitorelectrical data is shown below in Table 1:

TABLE 1 Filter Capacitor Electrical Data @ 100 MHz Oxidized TitaniumOxide-Resistant Filter Surface* Surface** Attachment ESR IL ESR ILSample 1 1.48 Ω 23.95 dB 0.467 Ω 28.82 dB Sample 2 1.49 Ω 23.91 dB 0.422Ω 29.08 dB Sample 3 3.86 Ω 17.30 dB where: ESR = Equivalent SeriesResistant IL = Insertion Loss *see FIGS. 6D and 6E **see FIGS. 6J and 6K

FIGS. 13A, 13B and 13C illustrate an internally grounded prior artfeedthrough capacitor. In general, internally grounded feedthroughcapacitors are known in the prior art with reference to U.S. Pat. Nos.5,905,627; 6,529,103; 6,765,780 and the like, all of which are fullyincorporated herein by reference. Referring once again to FIG. 13A, onecan see an internally grounded feedthrough capacitor, which is octapolar(eight active leads). The eight active leads are labeled 118 a through118 h on the body fluid side and on the inside of the AIMD housing theyare labeled 118′a through 118′h. The ferrule 122 has a peninsulastructure 139, which is connected to an internal ground pin 118gnd.Referring now to the octapolar feedthrough capacitor active electrodeplates 134, they are designed to overlay in a sandwich fashion theground electrode plates 136. One skilled in the art will realize thatone can stack up as many of these interleaved layers as is required inorder to achieve the required capacitance value and other designfactors. The internal ground lead 118gnd is electrically connected tothe ground electrode plate layers 136. The active electrodes 134 athrough 134 h are each electrically connected through their respectiveleadwires 118′a through 118′h. The overlap between the active electrodes134 and the ground electrodes 136 create what is known as effectivecapacitance area. The active and ground electrode layers may beinterleaved with additional ceramic layers to build up the dielectricthickness (not shown). In general, the monolithic ceramic feedthroughcapacitor 124, as shown in FIG. 6 as element 124, is a result oflaminating the various electrode layers together and then sintering themat a high temperature to form a rigid monolithic ceramic block. This isknown as a single feedthrough capacitor that is multipolar (in this casethese are octapolar or eight active filtered circuits). One can see thatthere is a perimeter metallization 132 on the outside of the roundcapacitor from FIGS. 3 and 7 whereas, in this case in FIG. 6 , there isno perimeter metallization 132 at all.

There are several major advantages to internal grounding and removal ofthe perimeter or diameter metallization 132. This is best understood byreferring back to FIGS. 3 through 8 . In contrast to FIG. 4 , withinternal grounding there is no longer a need to apply a diametermetallization 132 as shown in FIGS. 13A, 13B and 13C. In addition, theelectrical connection 148 has been entirely eliminated between thecapacitor diameter metallization 132 and the gold braze 140 and ferrule122. The elimination of this electrical connection 148 also makes thecapacitor structure 124′ much more resistant to mechanical damage causedby subsequent laser welding 128 of the hermetic seal assembly 116 intothe AIMD housing 102. A significant amount of heat is produced by laserwelding 128 and there is also a mismatch in thermal coefficient ofexpansion materials. By elimination of the electrical connectionmaterial 148, the capacitor 124′ is free to float and is therefore, muchmore resistant to such stresses. Referring once again to FIG. 13B, onecan see that the internal ground lead 118′gnd makes a low impedanceconnection from the capacitor's internal electrode plates 136 to theferrule 122. This is what eliminates the need for the electricalconnection material 148, as previously illustrated in FIG. 4 . It isappreciated that only one ground pin is shown in FIG. 6 , but somedesigns may require a multiplicity of ground pins spaced apart suchthat, there is a very low impedance connection effectively grounding thecapacitor internal electrodes 136 at multiple points.

Referring once again to FIG. 13B, one can see the ceramic capacitorsubassembly 124′ is ready to be installed onto the hermetic terminalsubassembly 189. These are shown joined together in FIG. 13C resultingin a hermetically sealed feedthrough capacitor filter assembly 116.

Referring back to FIG. 13B, it is important to clarify some confusion asterms of art. The feedthrough capacitor 124′ can also be described as athree-terminal feedthrough capacitor with multiple via holes orfeedthrough holes. In a confusing manner, the hermetic terminalsubassembly 189 is often referred to in the art as a hermeticfeedthrough. Therefore, we have the term feedthrough applying both tothe feedthrough capacitor and to the hermetic terminal assembly. As usedherein, these are two separate and distinct subassemblies, which arejoined together in FIG. 13C to become a feedthrough filter hermeticterminal assembly 116 ready for installation into an opening of an AIMDhousing. Referring once again to FIGS. 13A and 13B, one will appreciatethat leadwires or lead conductors 118′, 118 are continuous leadwires. Inother words, on the body fluid side, the leadwire is of the samematerial as on the device side. This is typical in the prior art.Referring once again to FIG. 13B, one can see that the internal groundlead 118′gnd does not extend through to the body fluid side of thehermetic terminal feedthrough subassembly 189. It is appreciated that itcan be easily and readily extended to the body fluid side, but in mostembodiments, it is not necessary.

An issue with the use of platinum for hermetic terminal subassemblyleadwires 118 a-d is that platinum has become extremely expensive andmay be subject to premature fracture under rigorous processing such asultrasonic cleaning or application use/misuse, possibly unintentionaldamaging forces resulting from Twiddler's Syndrome. Accordingly, what isneeded is a filtered structure like a feedthrough capacitor assembly 116which eliminates these high-priced, platinum, platinum-iridium orequivalent noble metal hermetic terminal subassembly leadwires 118. Foradditional examples of hermetic terminal subassemblies with feedthroughcapacitors that employ leadwires 118, one is referred to U.S. Pat. Nos.5,333,095, 5,896,267, 5,751,539, 5,905,627, 5,959,829, 5,973,906,6,008,980, 6,159,560, 6,275,379, 6,456,481, 6,529,103, 6,566,978,6,567,259, 6,643,903, 6,765,779, 6,765,780, 6,888,715, 6,985,347,6,987,660, 6,999,818, 7,012,192, 7,035,076, 7,038,900, 7,113,387,7,136,273, 7,199,995. 7,310,216, 7,327,553, 7,489,495, 7,535,693,7,551,963, 7,623,335, 7,797,048, 7,957,806, 8,095,224, 8,179,658, thecontents of which are fully incorporated herein by reference.

FIG. 13D is the electrical schematic for the feedthrough filteredhermetic terminal 116 previously described in FIGS. 13A, 13B and 13C.Referring once again to FIG. 13D, one can see the telemetry pin T, whichpasses through the filtered hermetic terminal assembly 116 without anyappreciable capacitance to ground. In other words, it would beundesirable to have any high frequency filtering of the telemetryterminal since this would preclude the ability to recover storedinformation or program the AIMD device remotely. Leadwires 118 a through118 h all have feedthrough capacitor hermetic terminal assemblies 116,124 as shown. The internal ground pin 118gnd is shown only on the deviceside of the hermetic terminal subassembly 189. Referring once again toFIGS. 13A, 13B, 13C and 13D, it is noted that the feedthrough filterhermetic seal subassembly has been inverted with reference to FIGS. 2, 3and 4 . It should also be noted that the capacitor 124 is still on thedevice side; it's just drawn inverted.

The internally grounded feedthrough capacitor illustrated in FIGS. 13A,13B and 13C has a ground connection through an internal ground pin118′gnd. This ground pin is ideally of platinum or similar noblematerial that is highly resistant to oxidation. Referring to theschematic diagram FIG. 13D for the filter of FIG. 13C, it is noted that,once again, the filters have no resistance in a system ground 144connection 102, 122, and are essentially ideal filters. Referring onceagain to the internally grounded filter of FIGS. 13A, 13B and 13C, thereis a disadvantage to the single ground pin 118′gnd. Such a design havinga single ground pin central to an elongate feedthrough capacitor asshown can cause undesirable inductance build-up across the feedthroughcapacitor ground electrode plates. In order to overcome this effect,several internal ground pins 118′gnd can be added. Another way to lookat this is that pins closest to the internal ground pin 118′ would havea higher insertion loss, in comparison to the pins most distant from it,such as pin 118′h.

FIG. 14 illustrates a prior art monolithic ceramic capacitor 194. Theseare otherwise known as MLCC chip capacitors. Multilayer ceramiccapacitors are very well known in the prior art and are produced dailyin the hundreds of millions. It is appreciated that MLCC chip capacitorsare also commonly referred to as multilayer ceramic capacitors ormonolithic ceramic capacitors. MLCC chip capacitors are commoncomponents in most electronic devices, including computers, modern smartphones and the like. It should be noted here that not all rectangulartwo-terminal capacitors, as illustrated in FIG. 12 , must be ceramic. Asused herein, MLCC ceramic chip capacitors shall also include all kindsof stacked tantalum, stacked film and other dielectric type capacitorsthat form two-terminal rectangular shapes. It will also be appreciatedthat any of the two-terminal capacitors in the art, including ceramic,film and tantalum can also have other shapes other than rectangular,including cylindrical and the like.

FIG. 15 , taken from section 15-15 from FIG. 14 , illustrates across-section of an MLCC chip capacitor. As can be seen, the prior artMLCC chip capacitor is a two-terminal device having a metallization onthe left 130 and a metallization on the right 132. It has overlappingelectrodes as illustrated in FIGS. 15A and 15B. It has an effectivecapacitance area created by the overlap of the left-hand electrodes 134with the right-hand electrodes 136.

FIGS. 16, 17 and 18 illustrate prior applications of MLCC chipcapacitors 194 attached to hermetic seal subassemblies of activeimplantable medical devices. These patents include: U.S. Pat. Nos.5,650,759; 5,896,267; 5,959,829 and 5,973,906, the contents of which arefully incorporated herein by reference. Referring once again to FIG. 16, the electrical connection between MLCC chip capacitor groundtermination 132 and circuit trace 147 is generally oxide-resistant;however, the attachment of the ground circuit trace 147 to the oxidizedferrule 122, which can become an electrical resistance problem. Aspreviously described in the prior art, an undesirable increasedresistance due to oxide thickening can seriously, even dangerously,degrade MLCC chip capacitor filter performance.

Referring once again to FIG. 17 , one can see that there is a hermeticseal insulator 120,188 disposed within a ferrule 122. In FIG. 17 , theinsulator 120,188 is hermetically sealed by a gold braze 140 between theinsulator 120,188 and ferrule 122. There is also a leadwire 118, havingbody fluid side lead end 118 and device side lead end 118′. Leadwire 118is continuous from the body fluid side to the device side. There is alsoa hermetic seal gold braze 138, which hermetically seals the leadwire118 to the insulator 120,188. Throughout this specification, it isunderstood that the insulator 120,188 is sometimes single-numbered as120, sometimes single-numbered as 188 or in some cases, is labeled120,188. It will also be appreciated that the gold braze insulator istypically of a high purity alumina ceramic. It is also appreciated thatthe insulator can include a glass or a glass-ceramic hermetic seal inwhich case, the gold brazes 138 and 140 are not necessary (therefore,there are no hermetic seal gold brazes for an oxide-free EMI filtersystem ground connection).

Referring once again to FIG. 18 , the left-hand side of the MLCC chipcapacitor 194 is electrically connected 143 directly to the potentiallyoxidized ferrule 122. As was just described for feedthrough capacitors,this is also very poor practice which can lead to undesirable resistancein series with the capacitor filter 194.

FIG. 18A is a sectional view taken from section 18A-18A from FIG. 18 ,which shows the MLCC chip capacitor 194 ground electrode plates 134 andactive electrode plates 136. It is appreciated that this symmetricalcapacitor can be reversed thereby reversing the ground and activeelectrode plates. The MLCC chip capacitor has capacitor terminationmaterials 132, as indicated, which are electrically connected usingelectrical connection material 143 directly to the ferrule 122. One cansee the undesirable surface oxide 164 that can form during laser weldingof the ferrule 122 and the device housing 102 as previously disclosed.The schematic diagram of FIG. 18A shows undesirable resistance R, whichis a result of this undesirable surface oxide 164. As previouslydescribed, the dielectric loss is also a series resistance, but at highfrequency, the series resistance will essentially go away.

FIG. 18B gives the equations for capacitive reactance and also forimpedance. ESR can undesirably increase the filter capacitor'simpedance, which is preferably as low as possible.

FIG. 18C further illustrates that the ohmic loss resistance due tosurface oxides 164 appear in series with the filter capacitor and systemground 144. This resistance is highly undesirable because it degradesfilter performance.

FIG. 19 illustrates a prior art flat-thru capacitor 400. This is betterunderstood by referring to its internal electrode plates as illustratedin FIG. 20 . The flat-thru capacitor of FIG. 19 is also known as athree-terminal capacitor because there is a circuit current i₁ thatpasses through its active electrode plate 412 from the first terminal184 to the second terminal 186. If there is a high frequencyelectromagnetic interference signal being conducted along this activeelectrode plate 412, then this electromagnetic interference is divertedthrough filter capacitance action to system ground at terminal 3.Referring back to FIG. 19 , there is a general disadvantage to suchcapacitors in that, at very high frequency, EMI 188 can cross-couplefrom the left side of the MLCC chip capacitor to the right side of theMLCC chip capacitor.

Referring once again to FIG. 19 , one can see a connection to systemground 144 (ground symbol), which is essential for proper filterperformance. As previously described, it is important that this systemground connection be essentially free of undesirable surface oxides.

FIG. 20 illustrates the ground and active electrode plates of theflat-thru capacitor 400 of FIG. 19 . The ground electrode plates are 414and the active electrode plate is 412. These electrode plates arestacked in interleaved relationship forming the flat-thru capacitor. Asshown, the circuit current i₁ passes through the active electrode plate412. There is an advantage to this in that any inductance along thelength of the plate appears in series with any EMI thereby improvingfilter efficiency. A downside of having the current pass through theactive electrode plate 412 is the limited current handling capability ofthe flat-thru capacitor active electrode plates. Flat-thru capacitors,as illustrated in FIGS. 19 and 20 , are acceptable for most activeimplantable medical device applications; however, this configuration ishighly unlikely for an implantable defibrillator, wherein a very highcurrent, high voltage shock must be delivered. The cross-sectional areaof an electrode plate 412 of a monolithic ceramic capacitor is generallylimited in cross-sectional area.

FIG. 21 also illustrates three X2Y attenuators 500 mounted on a circuitboard 147 that is designed to be placed adjacent to the device side ofan insulator and/or a ferrule of an AIMD hermetic seal subassembly.These X2Y attenuators are bipolar, meaning that each pair of X2Yattenuators filters two active leadwires, as shown. The X2Y attenuatorshave two active terminations 502 and 504 as shown. The X2Y attenuatorsalso have ground terminations 512 that must be electrically connected tosystem ground.

FIG. 22 illustrates the three X2Y attenuators of FIG. 21 mounted on thedevice side of insulator 120 and in a pocket of the ferrule 122.

FIG. 22A is a schematic diagram that illustrates each one of the X2Yattenuators. The X3 next to the schematic indicates that there are threeof these bipolar X2Y attenuators. Referring once again to FIG. 22A, onecan see that this X2Y attenuator 500 is disposed between adjacent activeleadwires One can see that there is line-to-ground capacitance betweenadjacent active leadwires 118 and also from each active leadwire tosystem ground. The X2Y attenuator forms line-to-line capacitance throughthe series capacitances between adjacent active leadwires 118 From anelectromagnetic interference (EMI) perspective, the line-to-groundcapacitance is useful for diverting differential-mode EMI, and theline-to-line capacitance is useful for attenuating differential-modeEMI. An example of differential-mode EMI is an EMI signal that producesa voltage when measured adjacent leadwire to leadwire 118. Thisdifferential voltage is best measured without the X2Y filter 500present. By careful design of the X2Y attenuator internal electrodeplates, one can control the amount of capacitance to ground and also theamount of line-to-line capacitance. The electrical schematic of FIG. 22Aassumes that the ground electrical connections are to a non-oxidizedferrule 122 surface, such as the gold braze 138 that is formed betweenthe ferrule 122 and the hermetic seal insulator 120. This is why thereis no resistance shown in the system ground connections of FIG. 22A.

FIG. 23 illustrates a prior art filtered hermetic seal assembly. In thiscase, there is an MLCC filter circuit board 147. Disposed on the circuitboard are six MLCC chip capacitors 194. Accordingly, the MLCC filtercircuit board is disposed on a hermetic seal of an AIMD that has sixactive poles or leadwires. The leadwires on the left end and the rightend are labeled 118gnd. As will be explained, these pins areelectrically and mechanically connected to the ferrule 122, each pinproviding a ground connection to internal circuit board ground plates(not shown). As will be disclosed, these circuit board ground plates areextremely important so that EMI is reflected similarly to prior artfeedthrough filter capacitors.

FIG. 23A is taken from section 23A-23A from FIG. 23 . This is the topview of the circuit board of FIG. 23 showing the top view of the MLCCchip capacitors 194 a through 194 f.

FIG. 23B is taken from section 23B-23B from FIG. 23 illustrating atleast one internal circuit board ground plate 161 embedded within thecircuit board. The at least one internal circuit board ground plate 161is electrically connected to system ground 144 through the two groundpins 118′gnd that are electrically connected to the ferrule. The atleast one internal circuit board ground plate 161 comprises ground viaholes 163 a through 163 e that provide a ground electrical connection toeach of the six MLCC chip capacitors 194. Referring once again to FIG.23A, one can see that there are circuit board via holes 163 electricallyconnected to the ground metallization 130 of each of the MLCC chipcapacitors 194. An optional circuit trace is shown between the groundvia holes 163 and the MLCC chip capacitor ground termination 130. It isappreciated that the ground connection to the MLCC chip capacitor groundtermination 130 can be a direct electrical connection to the circuitboard via hole or through a circuit board circuit trace as shown. Foroptimal filter performance, the circuit trace length is as short aspossible to minimize series inductance. Referring once again to FIG.23B, one can see that the hermetic seal active leadwires 118′ passthrough the circuit board ground plate 161 in non-conductive relation.The embedded or exterior circuit board ground plate 161 can consist of amultiplicity of ground plates and including a ground platepreferentially disposed between the circuit board and the hermetic sealinsulator 120. This relatively wide set of one or more circuit boardground plates 161 provides a very low inductance path to divert EMI fromthe active leads 118 to system ground 144. In addition, the one or morecircuit board ground plates 161 effectively reflect or absorb radiatedelectromagnetic fields thereby preventing direct entry of EMI into theinterior (device side) of the AIMD housing. This reflection andabsorption of incident fields is very important at high frequencies, forexample, those in the frequency range of cellular telephones and otherwireless communicators from approximately 300 MHz to 3000 MHz.

FIG. 23C is a cross-sectional view taken from 23C-23C of FIG. 23illustrating an embodiment of the ferrule ground pin 118gnd. The groundpin 118gnd is shown electrically and mechanically connected to theferrule 122 by either a laser weld 128 or a gold braze 138. Ideally,ground pin 118gnd is of an oxide-resistant material, such as, but notlimited to, platinum. This makes for an essentially oxide-freeelectrical connection 143 to the circuit board internal ground plates156. In this case, there are two circuit board ground plates: aninternal circuit board ground plate, which is embedded in the circuitboard, and an external circuit board ground plate, which is disposed onthe bottom of the circuit board. It is understood that, while twocircuit board ground plates are illustrated in FIG. 23C, the circuitboard may have one circuit board ground plate, which can be disposedeither internal or external of the circuit board. it is also understoodthat there may be a multiplicity of embedded internal ground plateseither in combination with at least one external circuit board groundplate or without any external circuit board ground plates. Any circuitground plate may alternatively be a circuit trace. Referring once againto FIG. 23C, one will see that there is a circuit board via hole, whichhas a via hole metallization 145 that is spatially aligned over theground pin 118gnd. Throughout the present invention, via holes areprovided with some sort of a conductive or metallization layer on theinside diameters. It is understood by one skilled in the art that theinside diameter of circuit board via holes can be metal eyelets, plated,metallized, or the like. In each case, conductive or metallization layerof the via hole is electrically connected to one or more internal orexternal circuit board ground plates or circuit traces. In the case ofFIG. 23C, the circuit board metallization 145 makes electrical contactto the one internal and the one external circuit board ground plates 156as illustrated.

FIG. 23D illustrates an alternative embodiment of grounding circuitboard ground plates 156. In this case, a circuit board ground via hole163 is spatially aligned over the gold braze 140 that forms a hermeticseal between the insulator 120 and the ferrule 122 of the hermetic seal.By spatially aligning the ground via hole over the gold braze 140, onecan then make an essentially oxide-free electrical connection directlyto the hermetic seal gold braze using electrical connection material143, as shown. Electrical connection material 143 can be a solder, athermal-setting conductive adhesive or the like. Referring once again toFIG. 23D, illustrated is a metallization layer 150 disposed on theperimeter wall of the insulator 120. The metallization layer 150 is,generally, an adhesion/wetting layer that, during the brazing process,facilitates the flow of the gold braze 140. An electrical connection tothe gold braze hermetically sealing the insulator and the ferruleprovides a reliable low resistance, low impedance and stable groundconnection. Electrical connection to the hermetic seal gold braze 140additionally provides a very low and reliable stable resistance for thecircuit board system ground path.

FIG. 23E shows that an oxide-free electrical connection to the circuitboard ground plates 156 can also be achieved by an oxide-resistant metaladdition 218, which is either gold brazed, or laser welded 128 to theferrule 122. Typically, this metal addition is of an oxide-resistantmaterial, such as platinum.

FIG. 23F illustrates another method of forming an oxide-resistantelectrical connection 143 from the circuit board ground plates 156 tothe ferrule 122. In this case, there is a gold pocket-pad 250, whichacts like a swimming pool moat into which gold braze or equivalentmaterials are formed. This forms an oxide-resistant electricalconnection between the ferrule 122 and the circuit board ground edgemetallization 149 and in turn, to the circuit board ground plates 156.

FIG. 23G is similar to FIG. 23C in that there is an oxide-resistantground pin 118gnd, which is electrically and mechanically connected tothe ferrule 122 by a laser weld 128 or a gold braze 138. In this case,instead of grounding through a via hole, as illustrated in FIG. 23C,there is an electrical connection 143 from a circuit board ground edgemetallization 149 directly to the oxide-resistant ground pin 118gnd.Accordingly, this provides a very low resistance (low ESR) groundingpath to system ground 144. As previously defined, system ground 144 isthe AIMD housing 102 and is also equivalent to the system ground 144provided by the ferrule 122. Importantly, circuit board ground plates156 provide a low impedance path for the filters (an MLCC chip capacitor154, an X2Y attenuator 300, a flat-thru capacitor 400, and combinationsthereof) to divert dangerous EMI currents while at the same time,shielding the insulator 120 from direct penetration of high frequencyRE-radiated noise (EMI). Referring again to FIGS. 23C-23H, the circuitboard ground plates 156 can also be called circuit board ground shieldplates. In other words, the ground plates 156 not only provide a lowimpedance filter circuit diversion pathway to system ground, but alsoshield against radiated EMI. Referring once again to FIG. 23C, one cansee that the radiated EMI is reflected off filter ground electrodes.Circuit board shield plates or ground plates act in identical manner.Not shown is that these plates also absorb incident RF energy and thatthe capacitive action of the filter diverts the RF energy to the AIMDhousing 102, where it is harmlessly dissipated as a few milliwatts ofheat energy. This diversion prevents the EMI from dangerously reachingthe inside of the AIMD shielded housing 102, as illustrated in FIG. 23A.

FIG. 23H is very similar to FIG. 23F in that an oxide-resistant goldbond pad 250 has been provided in a ferrule pocket. In this case, acircuit board ground via hole 163 has been spatially aligned over thegold pocket-pad 250, such that an electrical connection 143 is made tothe oxide-resistant noble gold filling the pocket. In this way, circuitboard ground plates 156 have a very low resistance connection to systemground 144, which is ferrule ground 122. Gold pocket-pads are disclosedin U.S. Pat. No. 10,350,421, the contents of which are incorporatedfully herein by this reference. Gold pocket-pads may comprise otheroxide-resistant materials such as platinum. Noble metals, such as goldand platinum, are used as jewelry for this reason, as gold and platinumdo not tarnish or oxidize over time. The pocket-pad 508 may comprise anumber of other oxide-resistant materials, such as gold, gold alloys,rhodium, rhodium alloys, platinum, platinum alloys, platinum-iridiumalloys, palladium, palladium alloys, nitinol, cobalt-chromium alloys andcombinations thereof. A potential disadvantage of the gold pocket-pad asillustrated in FIG. 23H is the cost of forming the swimming pool-likepocket in the ferrule 122 and the cost of a substantially large quantityof gold or other suitable material, which is disposed and subsequentlyre-flowed (typically in a high temperature vacuum gold braze furnace) inthe pocket-pad.

FIG. 23I illustrates the schematic diagram for FIG. 23 showing that boththe inductance and the resistance are minimized such that an idealcapacitor having trivial series resistance R is formed, which resultsbecause R_(OXIDE) has been eliminated. In summary, the embodiments ofFIGS. 23A through 23H disclose that an oxide-resistant or oxide-freeelectrical connection can be formed, therefore, there is no need for aresistor symbol R in the schematic of FIG. 23I.

FIG. 24 is similar to FIG. 23 , except that FIG. 24 illustrates a priorart circuit board 147 having circuit board ground edge metallizations149 electrically connected to circuit board ground plates (not shown),which are directly electrically connected 143 to the ferrule 122. Suchdirect electrical connection to the ferrule 122, as illustrated, isextremely poor practice. As previously described, the surface of atitanium ferrule is prone to the formation of resistive orsemi-conductive oxidation layers, which can significantly, evendangerously, reduce EMI filter performance. All of the same concepts aspreviously taught herein for feedthrough capacitors, apply to filtercircuit boards, including the filter circuit board of FIG. 24 . Aspreviously described, oxide removal by mechanical or acid etching of thetitanium ferrule 122 is only temporary, as oxides will almostimmediately reform. These oxides form very quickly at elevatedtemperatures, such as the high temperatures created by laser welding 128the ferrule 122 into an opening in an AIMD housing 102 (not shown).

FIG. 24A is taken from section 24A-24A from FIG. 24 illustrating thatthe ground electrical connection material 143 is disposed on the circuitboard ground edge metallization 149 and directly on the surface of theferrule 122, which, as previously disclosed, is not good practice. Forsimplicity, FIG. 24A does not show an oxide layer; however, theinventors of the present application have reproducibly demonstrated thateven curing a thermal-setting conductive adhesive 143 in a vacuum (ahard vacuum, which is a very difficult process) in an attempt to preventthe titanium ferrule 122 from reforming any oxides proved futile. Areproducible, stable and oxide-free connection was just not achievable.It is further noted that the electrical connection 143, as illustratedin FIG. 24A, cannot even be made using a solder, since a titaniumferrule 122 is not solderable because solders do not wet to titanium.

FIG. 24B is taken from section 24B-24B from FIG. 24 and illustrates theundesirable formation of an oxide layer 164 on the surface of a ferrule122. It is appreciated, that the surface oxide layer 164 would generallyoccur over all surfaces of the ferrule but is only shown on the top forsimplicity. As previously discussed, the surface oxide layer 164 greatlyincreases the resistance or equivalent series resistance (ESR) to thecircuit board ground plates 156 and then in turn, to the MLCC chipcapacitors 194 (not shown). Referring once again to FIG. 24A, thesurface oxide layer 164, shown in FIG. 24B, formed or re-formed or bothunderneath the electrical connection 143, in other words, between theelectrical connection material 143 and the previously cleaned ferrule122. As previously described, the electrical connection material 143, isa thermal-setting conductive adhesive, including conductive polyimides,conductive polymers and conductive epoxies. The surface oxide layer 164can be present at the time electrical connection material 143 is appliedor the surface oxide layer can form over time (later) between theferrule and electrical connection material 143, particularly duringlaser welding 128 of the ferrule 122 to the AIMD casing 102. Whenconducting a laser weld 128, substantial localized heat may begenerated, which can accelerate surface oxide layer 164 formation.

It is incorrectly believed by some that surface oxide layer 164 will notform on titanium components internal to the AIMD casing 32 once the AIMDcasing is hermetically sealed, because the area inside of an AIMDhousing is generally evacuated with a vacuum and then backfilled withinert gas, such as helium, nitrogen or argon, with the intention ofeliminating moisture. The belief that vacuum evacuation and back-fillingwith inert gas will inhibit oxidation of sensitive materials liketitanium is erroneous. Materials of construction used in the manufactureof AIMDs, such as polymers, plastics, adhesives, elastomers and thelike, and even the printed circuit boards (PCBs) themselves, generallyhave some level of gases trapped within their structure; for example,moisture, oxygen, other oxygen-containing gases, or even undetectedresidues comprising the same, which eventually outgas during theoperating life of the device. Furthermore, processes that do involveincreased temperature, like welding, curing or other temperature shifts,actually accelerate such outgassing. Hence, even if an AIMD ismanufactured in an inert gas environment, or backfilled with an inertgas, such ‘heating’ of certain materials of construction can releaseoxygen, oxygen-containing gases or water vapor into an otherwisehermetically sealed environment, causing the formation of surface oxidelayers 164 on otherwise conductive titanium surfaces 102, 122. It isextremely important that no undesirable surface oxides form in thesystem ground connection to any EMI filter. It is also important duringa qualification and during production, that filter performance metricsbe measured. These filter performance metrics must include: EquivalentSeries Resistance (ESR) above 10 MHz and, in particular, at 64 MHz (MRIRF pulsed frequency of a 1.5T scanner), and insertion loss (IL) sweepsin dB on a network analyzer from 10 MHz to 3000 MHz, including 64 MHz(1.5T MRI scanner) and 128 MHz (3T MRI scanner). For more detailreferring the effects of oxide layer formation on EMI filtering, referto the paper entitled, “Dissipation Factor Testing is Inadequate forMedical Implant EMI Filters and Other High Frequency MLCC CapacitorApplications”, ISSN: 0887-7491, presented at CARTS 2003: 23rd Capacitorand Resistor Technology Symposium, Mar. 31-Apr. 3, 2003, incorporatedherein by this reference. In summary, the presence of a surface oxidelayer 164 can seriously degrade EMI filter performance (in dB),particularly at high frequencies or at MRI RF-pulsed frequencies, wherethe diverter filters must bypass a substantial amount of high frequencycurrent. Accordingly, the inventors have found that thenon-oxide-resistant electrical ground connection, such as illustrated inFIGS. 27A, 27B, and 27C are a highly undesirable approach.

FIG. 24C is taken from section 24C-24C from FIG. 24 and illustrates theheat that is formed during laser welding 128 of the ferrule 122 into anopening of the AIMD housing 102. This heat undesirably does twothings: 1) it heats up the electrical connection material 143, which istypically a thermal-setting conductive adhesive. This heating of thepolymer releases free oxygen which then becomes available to form athicker surface oxide 164. As shown, a surface oxide layer forms allover the inside of the housing. As previously discussed, titanium oxideformations are accelerated by elevated temperature. Referring once againto FIGS. 248 and 24C, the surface oxide layer 164 may comprise severallayers, with any one or more layers further comprising one or moretitanium oxide compositions. As mentioned, these surface oxide layers164 are undesirably insulative and can also cause potentiallyundesirable semi-conductor behavior. One approach that the inventorshave tried in the past is to clean the oxide layers 164 from the ferrule122 device side surface using abrasive mechanical and chemical removalprocesses, including grit-blasting, mechanical grinding, sanding, andhydrofluoric acid cleaning. It should be noted that titanium oxides,once formed, are very stable and very hard to remove. Titanium oxidesare so stable that they are commonly used as paint pigments. Referringonce again to FIG. 24A, the inventors first cleaned the oxide layers 164from the device side ferrule 122 surface and then formed a stripe or acoating of an electrically conductive adhesive (ECA stripe 223′). TheECA stripe 223′ comprised a thermal-setting conductive polyimide. Duringthis experiment, there was no oxide-resistant sputter layer 165, inaccordance with the present invention. In other words, the ECA stripe223′ was directly applied to the titanium surface 122. The inventorsthen connected the ground metallization of feedthrough filter capacitors124 directly to the ECA stripe 223′ with electrical connection material148, 143. This seemed to work very well in high frequency electricalmeasurements, including insertion loss (IL), impedance, ESR andinductance, all initially measuring very low and within acceptablespecification limits. However, as previously described in FIGS. 60, 6Eand 6F, out of a prototype qualification lot of a thousand piecesevaluated, five (post laser welding) parts exhibited higher resistancesand impedances, thus failed qualification testing. Graphs of ESR vs.frequency sweeps of three of these five failures are shown in FIGS. 6D,6E and 6F which alarmingly and dangerously show elevated high frequencyresistance due to oxide formation, particularly at 100 MHz. This high ofa failure rate (0.5%) for life sustaining devices like implantablecardiac pacemakers and ICDs is unacceptable.

FIG. 24D illustrates the schematic diagram of the filter circuit boardof FIG. 24A, FIG. 24B and FIG. 24C. Undesirably, R_(OXIDE) forms, whichcan either be immediate, latent or induced by thermal processes. Aspreviously described, the formation of this R_(OXIDE) seriously degradesEMI filter performance.

Referring to FIGS. 25 and 26 +, the inventors have conceived a novelconcept by which the ECA stripe 223 can be effective. To render the ECAstripe 223 effective, a low resistance and low impedance connection athigh frequencies to the ferrule 122 must be made. To achieve such a lowresistance and low impedance connection, especially for highfrequencies, two very important steps are required: Step 1) at least theferrule 122 device side surface must be cleaned of all oxides; and Step2) an oxide-resistant layer 165, as shown in FIGS. 25A and 26A, must bedisposed on the ferrule 122 device side surface at least in the area ofthe ECA stripe 223. As described previously, cleaning of the ferrule 122device side surface can be done mechanically or chemically by eitherabrasive grit blasting, such as by alumina blasting, mechanicalgrinding, sanding processes, hydrofluoric acid cleaning, or combinationsthereof, which would remove oxide layers from the ferrule 122, or atleast the ferrule device side surface. Once the ferrule 122, and inparticular, its device side top surface have been essentially cleaned ofoxides, time and temperature become important. If the cleaned ferrule isleft lying around at room temperatures, or worse yet, exposed toelevated temperatures, intentionally or unintentionally, these oxides164 will undesirably re-form. Accordingly, the inventors have tested anddetermined that an oxide-resistant layer 165, such as a noble metallayer, must be deposited soon after at least the ferrule 122 device sidesurface is cleaned of surface oxides. One preferred method of depositingan oxide-resistant layer 165 on the ferrule 122 device side surfaceincludes sputtering, including sputtering of such materials as gold,platinum, rhodium, or palladium. As will be seen below, there are manyways of depositing the oxide-resistant layer 165. It should also bepointed out that the term ECA or electrically conductive adhesive stripe223 is also not meant to be eliminated. There are many other materials,as will be described herein, that can be used in addition toelectrically conductive adhesives or ECA stripes. As previouslydescribed, the ferrule 122 device side surface must be cleaned of allsurface oxides immediately prior to deposition of the oxide-resistantlayer 165. Preferably, sputtering, and other processes to deposit layer165, is performed in a vacuum chamber. This also includes firstdepositing an optional barrier layer between oxide-resistant layer 165and the ferrule device side surface 122. Other ways of disposing anoxide-resistant layer is by physical vapor deposition, chemical vapordeposition, electrostatic spray assisted vapor deposition (ESAVD),electron beam physical vapor deposition (EBPVD), ion plating, ion beamassisted deposition (IBAD), magnetron sputtering, pulsed laserdeposition, sputter deposition, vacuum deposition, pulsed electrondeposition (PED), plating, electroless plating, electroplating,spraying, painting, plasma spraying, thermal spraying, spin coating, dipcoating, metal foil lamination, and thin film deposited layers, eitherfully or selectively disposed. The electrically conductive coating maycomprise one or more layers. These processes may be used to depositmaterials such as gold, gold alloys, rhodium, rhodium alloys, platinum,platinum alloys, platinum-iridium alloys, palladium, palladium alloys,nitinol, cobalt-chromium alloys and combinations thereof. Additionally,selective electro-plating can be used. For example, a layer of nickel(example, see FIG. 31 element 166) would first be deposited on top ofthe essentially oxide-free titanium surface at least in the area ofwhere the ECA stripe 223 is intended to be deposited on the ferrulesurface device side 26′. Then, an oxide-resistant layer 165, such as alayer of gold, platinum, rhodium, or any of the materials disclosedabove, is plated on top of an optional nickel layer. The purpose of thenickel layer is to prevent titanium from migrating through anoxide-resistant layer. For example, a thin film pure gold layer ishighly resistant to forming oxides and is highly conductive. However, athin film gold layer may be relatively “porous”, which can allowtitanium to migrate through the thin film gold layer to its free (top)surface. Researchers have shown that, when a thin film gold layer isdisposed on an essentially oxide-free titanium surface, the titanium candiffuse along the grain boundaries at the gold/titanium interface to thefree surface of the thin film gold layer, where the titanium isoxidized. Accordingly, laying down a layer of nickel or other suitablematerial that prevents migration of titanium through it, is required. Inanother embodiment, the nickel layer can be omitted with a suitablythick layer of gold, platinum or the like, such that they sustainsurface oxide resistance.

FIG. 25 is a conventional externally grounded feedthrough capacitor 124similar to the feedthrough capacitor 124 previously described in FIG. 3, FIG. 4 and FIG. 7 . In this case, this is an inline 8-polar(octapolar) feedthrough capacitor. Ground electrical connections 143 aremade to an ECA stripe 223 which overlays an oxide-resistant sputterlayer 165 of the present invention. The ECA stripe 223, which overlaysthe oxide-resistant sputter layer 165 can be discrete pads or becontinuous along both long sides of the feedthrough capacitor or allaround its full perimeter. The inventors have found through analysis andtesting, that the ECA stripes 223 can be discontinuous, as illustrated,and still provide excellent high frequency EMI filter performance.

Oxide-resistant sputter layers 165 enable very low resistance andtime-stable electrical connections, which, in turn, provide very lowequivalent series resistance (ESR) electrical connections.Oxide-resistant time-stable electrical connections are very importantfor medical devices, particularly AIMDs, as the inventors havediscovered that, without oxide-resistant time-stable electricalconnections, highly reactive materials, such as titanium, can oxidizeover time, which can cause latent dangerous and unpredictable AIMD EMIfilter performance issues. More importantly, EMI filter failureresultant from oxide 164 build-up over time can be life-threatening. Ithas been shown in numerous articles that EMI can disrupt the properoperation of an AIMD. For example, if an EMI filter fails to filter in acardiac pacemaker, the EMI can then enter the housing of the pacemakerwithin which the therapy delivery circuitry resides. EMI inside thepacemaker can lead to improper therapy or even complete inhibition oftherapy to the patient. Inhibition of therapy from a cardiac pacemakerto a pacemaker dependent patient can be immediately life-threatening tothat patient. While a titanium oxide layer on the highly reactivetitanium metal surface imparts good corrosion behavior and highbiocompatibility, which is why titanium is used so extensively inmedical implantable devices. However, the titanium oxide layer 164 thatforms so readily on the titanium metal can and does negatively impactAIMD EMI filter performance, the negative impact being particularlyobservable at higher frequency applications, such as switchingapplications, coupling applications, bypass applications in addition toEMI filtering.

The term “oxide-resistant” is defined herein as the ability of asubstance to maintain its original material properties after beingexposed to oxygen; a resistance to oxidation under extreme conditionssuch as high temperature, essentially resists reaction with oxygen oroxygen-containing environments. The oxide-resistant sputter layer of thepresent invention comprises an oxide-resistant material 165 such asgold, platinum, palladium, silver, iridium, rhenium, rhodium, tantalum,tungsten, niobium, zirconium, vanadium, and combinations or alloysthereof. Some exemplary platinum-based oxide-resistant alloys for use inthe oxide-resistant sputter layers 165 of the present applicationinclude: platinum-rhodium, platinum-iridium, platinum-palladium, orplatinum-gold. Naturally occurring oxide-resistant alloys examplesinclude: platiniridium (platinum-iridium), iridosmium and osmiridium(iridium-osmium). Other oxide-resistant sputter layer alloys include:gold-based, platinum-based, palladium-based, silver-based, among others,wherein the metal-based element is the largest weight percent (>50%) ofthe total alloying elements of the alloy. Non-limiting noble metal-basedoxide-resistant alloys for use in the oxide-resistant sputter layers ofthe present application include: gold-palladium, gold-boron, andpalladium-silver. It is anticipated that proprietary oxide-resistantalloys such as but not limited to the Pallabraze product family(palladium-containing) and Orobraze product family (gold-containing)offered by Johnson Matthey may additionally be used to formoxide-resistant layers of the present application.

FIG. 25A is taken from section 25A-25A from FIG. 25 and illustrates incross-section, the ECA stripe 223 that overlays the relatively thinoxide-resistant sputter layer 165. In order for the sputter layer 165 tomake an oxide-free electrical connection to the titanium ferrule 122,the titanium ferrule 122 must be either mechanically cleaned bygrinding, abrasive grit blasting or even by chemical processes to makesure it is completely free of all oxides. Prior application of theoxide-resistant sputter layer 165, an optimal embodiment of the presentinvention, is to lay down a barrier layers 166 (FIG. 31 ), which cancomprise a very thin layer of nickel, palladium or even platinum. Thisprevents titanium oxides from coming to the surface, for example, if theoxide-resistant sputter layer 165 is gold. Other barrier layer optionsinstead of or in combination with nickel, palladium, and platinuminclude: rhodium, ruthenium, molybdenum, and chromium; alloys, such asnickel-vanadium, nichrome, nickel-iron, palladium-cobalt,cobalt-tantalum; nickel alloys, palladium alloys, platinum alloys; andelectrically conductive nitrides, such as titanium nitride, zirconiumnitride, hafnium nitride, vanadium nitride, tantalum nitride, molybdenumnitride, and tungsten nitride. The term “sputter layer 165” is hereindefined as a thin film or coating that covers a surface or surfaces of acomponent, an assembly, a substrate, a structure or an object. A sputterlayer 165 may comprise a single material or may alternately comprisemultiple materials. It is understood that a sputter layer may compriseone or more layers. Sputter layers 165 may be applied by one of thefollowing methods: physical vapor deposition, chemical vapor deposition,electrostatic spray assisted vapor deposition (ESAVD), electron beamphysical vapor deposition (EBPVD), ion plating, ion beam assisteddeposition (MAN, magnetron sputtering, pulsed laser deposition, sputterdeposition, vacuum deposition, pulsed electron deposition (PED),plating, electroless plating, electroplating, spraying, painting, plasmaspraying, thermal spraying, spin coating, dip coating, metal foillamination, and thin film deposited layers. Thin sputter layers 165 foroxide-resistant attachments benefit from thin film sputter layer“stackup” systems that inhibit metal and/or oxide migration through theoxide-resistant layer, as such oxide migration through theoxide-resistant layers can eventually result in brittle connections formetal migrations and/or increased electrical connection resistance foroxide migrations. Both are undesirable, as either one independently orin combination comprise the reliability and integrity of the electricaland mechanical connections. Barrier layers provide the followingbenefits to AIMD component mechanical and electrical connections: (1)prevents inter-diffusion of metals up or down through the sputter layerstackup system which can compromise mechanical connection integrity;and, (2) prevents migration of oxides up or down through the sputterlayer stackup system, which can compromise electrical integrity. As anexample, when an essentially pure gold metal is used as theoxide-resistant sputter layer, a preferred sputter layer stackup systemcomprises one or more barrier layers atop of which the gold sputterlayer 165 is applied. Then the ECA stripe 223 can be applied thereonproviding a reliable mechanical and low resistance low ESI electricalconnection. A barrier layer 166 (FIG. 31 ) having a thickness of 100Angstroms to 4000 Angstroms (0.01 micron to 0.4 microns; 10 nm to 400nm), depending on the metal selected, is sufficient to provide robustmechanical and reliable electrical connection. In some cases, thebarrier layer may comprise two or more layers, each layer having apreferred thickness to achieve an overall barrier layer stackupthickness of about 100 Angstroms to about 4000 Angstroms (0.01 micron to0.4 microns; 10 nm to 400 nm).

A barrier layer 166 (FIG. 31 ) is an optional consideration foroxide-resistant sputter layers 165 applied to a titanium surface.Deciding to include a barrier layer is dependent on the stability oftitanium in contact with the oxide-resistant sputter layer. Using a goldoxide-resistant sputter layer on a titanium surface as an example, it isknown that at elevated temperatures, titanium (Ti) can interdiffuse withthe gold (Au) to either form a Ti—Au intermetallic, or, the titanium canactually diffuse to the free surface of the gold to form titaniumoxides, which in turn can cause undesired ohmic resistance. In general,interdiffusion of thin films occur by way of lattice defects in theatomic structure of a material, for example, vacancies, dislocations andgrain boundaries. For the Ti—Au system, titanium atoms diffuse into thegold typically in the grain boundaries, thereby either formingintermetallics, such as TiAu₄, TiAu₂, TiAu, and Ti₃Au, or diffusing upto the gold free surface to react with oxygen thereby forming bothanatase and rutile titanium dioxide TiO₂. Of significance is that Tidiffusion to the Au free surface can occur at processing temperatures aslow as 200° C. to 400° C. Because surface oxidation of titanium occursat the gold free surface, the titanium oxidation reaction itself createsa chemical potential sink, which continually drives diffusion of thetitanium through the gold, thereby supporting and enhancing a continuoustitanium oxidation process. Since oxygen enhances diffusion of the Ti—Ausystem, the very rapid diffusion of the titanium through the gold layerand the formation and thickening of the titanium oxide at the freesurface explains the undesirable increase in ohmic resistance over time.

Referring once again to the Ti—Au system, providing a barrier layer 166between the titanium 102 and 122 and the gold can prevent titaniummigration to the free surface of the gold layer 165. The barrier layer166 must, however, be stable at typical AIMD processing conditions andthe barrier layer 166 must effectively suppress titanium diffusion. Asan example, a palladium (Pd) barrier layer 166 between the titaniumsurface and the gold can sufficiently suppress titanium diffusion.Researchers have shown that, even after annealing Ti—Pd—Au test samplesin air, no diffusion of titanium is evident in this three-layer system.The suppression of titanium diffusion is likely due to a rapid grainboundary diffusion of gold in the palladium grain boundaries, which arethereby effectively blocked by gold, hence, this particular Pd—Auinteraction therein completely suppresses any substantial migration anddiffusion of the titanium. Thus, the optional barrier layer 166 providesan effective alternative for sustaining sputter layer 165oxide-resistance, as such barrier layers 166 can effectively suppresstitanium diffusion to and subsequent oxidation at a free (top) metalsurface 165.

As illustrated in FIG. 25A, once the thin sputter layer has beendeposited 165, then an ECA stripe 223 is applied. The ECA stripe, asdefined herein, may comprise one of: a thermal-setting electricallyconductive adhesive, an electrically conductive polymer, an electricallyconductive epoxy, an electrically conductive silicone, an electricallyconductive polyimides, or an electrically conductive polyimide, such asthose manufactured by Ablestick Corporation. An oxide-free electricalconnection 143 is then formed between the ECA stripe 223 and the groundmetallization 132 of the feedthrough capacitor. Electrical connectionmaterial 143 may comprise a solder or a second thermal-settingconductive adhesive. In an embodiment, the thermal-setting conductivematerial for the ECA stripe 223 can be the same material as theelectrical connection material 143. The ECA stripe 223 of the presentinvention provides a robust connection therefore, allowing therelatively expensive sputter material 165 to be relatively thin. Forexample, it would not be possible to solder directly to very thinsputter layer 165 as the sputter layer would simply dissolve into themolten solder. For a thermal-setting conductive polyimide, it is alsodifficult to make a mechanically robust connection to such a thin layer165 without first depositing an ECA 223 stripe over it. By depositingthe ECA stripe over the sputter layer 165 and then curing it, withoutthe feedthrough capacitor, one minimizes strains and stresses due tomismatches in coefficients of thermal expansion. Accordingly, adding theelectrical connection 143 in a subsequent operation becomes veryreliable and easy to accomplish. The feedthrough capacitor 124 isgenerally disposed against the insulator 122 with an optional insulativewasher 206, as shown in FIG. 25A.

Referring once again to FIG. 25A, it is understood that both the sputterlayer 165 and the ECA stripe 223 are proud of the surface of the ferrule122. This is in marked contrast to the gold pocket-pads 250 as taught inU.S. Pat. No. 10,350,421. One is referred to the gold pocket-pad 250 ofFIG. 23F herein. To form the gold pocket-pad, as described in U.S. Pat.No. 10,350,421, the contents of which are incorporated herein fully byreference, one must first form a recess or pocket in the ferrule itself.This swimming pool-like structure is formed or machined into theferrule. The gold pocket-pad of the U.S. Pat. No. 10,350,421 inventionrequires that a gold braze (or equivalent) preform be disposed into thepocket-pad, and reflowed. Reflow of a gold braze preform is normallyperformed in a high temperature gold braze furnace. Forming of thepocket-pad is a relatively expensive process and also the amount of gold250 that is required to form a robust pocket-pad, is also substantialand expensive. In the present invention, there is no need for a recessedpocket or swimming pool-type structure in the ferrule 122 at all.Instead, a sputter layer 165 is disposed proud or on the top of theferrule, over which the ECA stripe 223 is formed.

FIG. 26 is a filter circuit board 147 with one or more embedded circuitboard ground plates that is similar to FIG. 24 . However, referring toFIG. 26 , one can see that in accordance with the present invention,disposed on top of the ferrule, is oxide-resistant sputter layer 165with the ECA stripe 223 of the present invention disposed on top. Thereis an electrical connection using electrical connection material 143formed between the ECA stripe and the ground edge metallization 149 ofcircuit board 147.

FIG. 26A is taken from section 26A-26A from FIG. 26 and shows a blow-upview of the electrical connection 143 between the circuit board groundtermination 149 and the ECA stripe 223 which rests on top of theoxide-resistant sputter layer 165.

FIG. 27 is taken from section 27-27 from FIG. 26 and shows the top viewof the circuit board of FIG. 26 . One can see the top view of the ECAstripe 223, the electrical connection material 143 and theoxide-resistant sputter layer 165. The hidden lines 156 illustrated inFIG. 27 , show the edge of at least one embedded circuit board groundshield plate.

FIG. 28 is taken from section 28-28 from FIG. 26 and in this cutaway,shows the circuit board ground plate 156. It is appreciated that thereis at least one of these ground plates, but there may be a multiplicityof these ground plates 156, including embedded ground plates or oneexternal ground plate disposed between circuit board 147 and ferrule122. Importantly, the ground plate 156 is disposed over the hermeticseal insulator 120 thereby blocking direct penetration of EMI into theinterior of the AIMD housing 102. As described, one or more groundplates 156 effectively shield and provide a low impedance path todecouple dangerous EMI signals to the system ground 144. The circuitboard ground plates of the present invention are also known as groundshield plates.

FIG. 29 is taken from section 29-29 from FIG. 26 and illustrates a cutthrough the first row of MLCC chip capacitors. Referring once again toFIG. 29 , one can see that there is an embedded ground shield plate 156and an external ground shield plate 156′ which is disposed between thebottom of the circuit board 147 and the top of the insulator 120. Theexternal ground shield plate 156 is ideal since this space is as closeto the insulator 120 as possible. This prevents waveguide action whereinradiated EMI can couple or radiate through the edge of the circuit board147.

FIG. 30 is taken from section 30-30 from FIG. 26 and illustrates acutaway right through the center of the active terminal pins of the AIMDcircuit board 147. Leadwires or pins a, b and c have conventional goldbrazes that hermetically seal the pins to the hermetically sealedinsulator 120. As can be seen, the circuit board 147 and its associatedMLCC chip capacitors 194 are oriented towards the device side of theAIMD. Gold brazes associated with pins a, b and c, are disposed on thebody fluid side. Pin d is very similar to the gold brazes 138 for a, band c, which are disposed on the body fluid side. On pin d, the goldbraze 138′ is disposed toward the device side. There is an advantage indisposing the gold braze 138′ on the device side. That is, if pin d is aheavily oxidized pin, such as a niobium or tantalum pin, then a directelectrical connection can be made from the circuit board via associatedwith gold braze 138′ such that an oxide-free electrical connection ismade between gold braze 138′, leadwire d and the MLCC chip capacitorground termination. This is very important as it allows the use of verylow-cost terminal pins. Terminal pin e embodies the terminal pin post118′ disposed on a co-sintered via. In this case, the co-sintered viasare taught by U.S. Pat. No. 10,249,415, the contents of which are hereinincorporated fully be reference. One is referred to FIG. 131 of the '415patent for various embodiments of co-sintered vias. Referring once againto FIG. 30 , there is a substantially pure platinum center core 186,which is surrounded by ceramic reinforced metal composite (CRMC).Referring once again to FIG. 30 , terminal pin f is a 2-part pin astaught by U.S. Pat. No. 10,272,251, the contents of which areincorporated herein fully by reference. Pin f allows a relativelyinexpensive tantalum, niobium or titanium pin 118″ to be disposed on thebody fluid side, which is then co-brazed 138′, such that a shorterpalladium or platinum iridium pin 118′″ is disposed toward the deviceside. These are thoroughly taught in the '251 patent. Another advantageof the construct in pin f is that the gold braze 138′ is disposedtowards the device side. This has the same advantage as that previouslydescribed for pin d that would allow an oxide-resistant connectiondirect to the gold braze 138′. Referring once again to FIG. 30 pin e,one will also appreciate that materials 185 and 186 can be combined insubstantially pure platinum 186 as taught in U.S. Pat. No. 8,653,384 andits entire family. These are substantially pure platinum co-sinteredvias with alumina insulators 120.

FIG. 31 is similar to FIG. 23H, except that the gold pocket-pad 250 hasbeen replaced by the ECA layer 223 and the oxide-resistant sputter layer165 of the present invention. In this case, circuit board 147 has aspatially aligned via hole that connects to its internal groundelectrode plates 156. This via hole 143 replaces an edge connection tothe circuit board. It is appreciated that any number of ground via holescan be used in this manner with corresponding ECA stripes 223 and theoxide-resistant sputter layers 165. Referring once again to FIG. 31 ,one can see that there is an optional barrier layer 166 that isrepresented by a thin black line between the oxide-resistant sputterlayer 165 and the ferrule 122. As previously described, this optionalbarrier layer can comprise of nickel or the like to block any oxides oftitanium from coming to the surface.

Referring back to FIG. 31 , it is appreciated that the electricalconnection material 143 can be a solid nail head structure. This is amachined or stamped pin or an eyelet. In the case that this was a solidmaterial, there is an electrical connection between this solid construct143 and the via hole metallization 145 (not shown). Referring once againto FIG. 31 , it is appreciated that spatially aligning a grounded viahole over the ECA stripe 223 and the oxide-resistant sputter layer 165of the present invention, is equally applicable to internally groundedfeedthrough capacitors 124′.

FIG. 32 indicates an embodiment of the present invention wherein theoxide-resistant sputter layer 165 is sufficiently robust that it canprovide an oxide-free electrical connection without the need for anoverlaying ECA stripe 223. In this case, the ferrule 122 is thoroughlycleaned, and then for example, a barrier layer of nickel, and then anoxide-resistant sputter layer of gold 165 can be applied. This goldlayer would have to be substantially thick so that a subsequentattachment of an electrical connection material 143 would not damage theconnection. For example, if electrical connection material 143 was ahigh lead content solder, then a gold sputter layer 165 would readilydissolve into the molten solder. Platinum, palladium and alloys thereofcan be used as barrier layers for gold, so that is molten solder doesdissolve in the gold, an oxide-resistant attachment to the titanium ispreserved. Alternatively, platinum, palladium and alloys thereof providean excellent alternative to gold layers altogether, as these materialsprevent both metal diffusion and migration, thus, titanium would not beable to reach the free metal surface, and then oxidize. Additionally,platinum, palladium and alloys thereof are also solderable. Thus, whilepreserving oxide-free electrical connection integrity, platinum,palladium and alloys thereof additionally prevent solder leaching of aeutectic or a soldered component, therein also preserving the mechanicalintegrity of the attachment. Moreover, neither palladium nor platinumthemselves form oxides or migrate easily.

Oxide-resistant sputter layers 165 may also be used to enablesolderability of titanium. In this case, an oxide-resistant solderablematerial in accordance with the present invention is disposed on acleaned titanium surface. Examples of oxide-resistant solderablematerials that can be disposed on titanium include gold, palladium,platinum, rhodium, and combinations and alloys thereof.

Referring once again to FIG. 32 , one will see that the groundtermination can be for a feedthrough capacitor, an internally groundedfeedthrough capacitor 124′, an MLCC chip capacitor 194, a flat-thrucapacitor 400 or an X2Y attenuator 500. It is very important that all ofthese EMI filters have a system ground connection 143 that is free ofoxides. The ground plate in FIG. 32 is any ground plate or groundelectrode or any of the filters above described. Accordingly, thetermination material that connects between the oxide-resistant sputterlayer 165 and the filter capacitor can be a connection either to afeedthrough capacitor outside diameter perimeter metallization 132, agrounding pedestal or location for an internally grounded feedthroughcapacitor 132, the ground terminations for a flat-thru capacitor, theground terminations for an X2Y attenuator, an ground edge metallization149 for any type of filter circuit board 147, or a metallization ortermination on the inside diameter of any circuit board or capacitivevia hole 145.

Referring to the ECA stripe 514 of FIG. it is contemplated that, forsome applications wherein ECA electrical connection may not be needed toprovide an electrical connection between at least two AIMD components,the ECA stripe 514 can be eliminated if the oxide-resistant layer(s) 516is/are robust enough to prevent titanium migration and oxidation,thereby allowing attachment of the electrical connection material 504directly to the oxide-resistant layer 516. As previously disclosed,platinum, palladium and alloys thereof are two such oxide-resistantlayer material options. In other words, either an oxide-resistant layercan be used to make the ECA stripe 514 an effective low resistance andlow impedance connection or the oxide-resistant layer(s) alone can beused instead of the ECA stripe 514. It is appreciated that the ECAstripe 514 and/or the metallization layer 516 may also be used toprovide suitable grounding, not just for circuit boards 106, 106′, butalso for all types of filter capacitors, including feedthrough filters24, 24′, hybrid feedthrough capacitors 24″, MLCC chip capacitors 154,X2Y attenuators 300, and flat-thru capacitors 400.

Referring once again to FIG. 32 , it is appreciated that directattachment of the ground electrical material 143 to a robustoxide-resistant sputter layer 165 is equally applicable to the groundvia hole of feedthrough capacitors 124 or internally groundedfeedthrough capacitors 124′, circuit board 147 edge, ground or via holemetallizations, MLCC chip capacitor 194 ground metallization, or theground metallization of flat-thru capacitors 400 or X2Y attenuators 500.Accordingly, the ground plate in FIG. 32 can be any ground plate orground electrode of any of the capacitors or filter circuit boards ofthe present invention.

FIG. 33 illustrates a prior art reverse geometry MLCC chip capacitor304.

FIG. 34 is taken from section 34-34 from FIG. 33 showing the internalelectrode plates of the reverse geometry MLCC chip capacitor 304. Theadvantage of the reverse geometry MLCC chip capacitor is greatly reducedinductance and superior high frequency filtering performance.

FIG. 35 shows the reverse geometry MLCC chip capacitor 304 mounted toferrule 122 using the novel ECA stripe 223 and the oxide-resistantsputter layer 165 of the present invention.

FIG. 36 is the schematic diagram of the reverse geometry MLCC chipcapacitor 304. Notably, no resistance or inductance is present in thisschematic as this configuration offers superior high frequency filterperformance at a very low impedance, Z.

FIG. 37 is a prior art quadpolar flat-thru capacitor 400′. It has fouractive terminations 402, 406 and two ground terminations 404, 404′.

FIG. 38 is taken from section 38-38 from FIG. 37 and illustrates theactive electrodes 412 a through 412 d. Also shown in the lower part ofFIG. 38 , are the set of ground electrodes 414. These are connected toterminations on the left side 404 and on the right side 404′.

FIG. 39 shows the quadpolar flat-thru capacitor 400′ of FIG. 37 attachedto ferrule 122. Attachment material 143 connects to the ECA stripe 123and in turn, to the oxide-resistant sputter layer 165. The electricalattachment material is connected to the flat-thru capacitor edgemetallization 404 as indicated. Flat-thru capacitor ground electrodeplates 414 are also indicated.

FIG. 39A shows the flat-thru capacitor 400′ of FIG. 37 mounted in atombstone position to an insulator and ferrule for an AIMD hermeticterminal assembly. One can see in this unique construct that theflat-thru capacitor ground terminations 404 are electrically connected143 to the ECA layer 223 and the oxide-resistant sputter layer 165 ofthe present invention. Referring once again to FIG. 39A, one can seevarious types of co-sintered vias that include a CRMC material and apure platinum material 186.

FIG. 39B illustrates the schematic diagram of the flat-thru capacitor ofFIGS. 37 and 39 . Referring once again to FIG. 39A, one can see that theflat-thru capacitor ground is connected to the ECA stripe and, in turn,to the oxide-resistant sputter layer 165 and then to ferrule 122.

FIG. 40 illustrates a prior art X2Y attenuator 500. As indicated, it hasactive metallizations 502 and 504 and ground metallizations 512.

FIG. 40A illustrates the two active electrode plates 506 and 508 of theX2Y attenuator. Terminations 502 and 504 connect to the active plates506 and 508.

FIG. 40B illustrates the X2Y attenuator ground electrode plate set 514.These ground electrode plates are connected to ground terminations 512,as shown.

FIG. 40C illustrates the entire X2Y attenuator with the ground electrodeplates 510 interleaved with the active electrode plates 506 and 508.

FIG. 40D is a sectional view of the X2Y attenuator 500 of FIG. 40attached to ferrule 122. As can be seen, the ground metallization 512 iselectrically connected 143 to the ECA stripe 223 and, in turn, to theoxide-resistant sputter layer 165 of the present invention. Referringonce again to FIG. 40D, one can see that the ground termination 512connects to the X2Y attenuator ground plates 510.

FIG. 40E illustrates the schematic diagram of the X2Y attenuator 500 ofFIGS. 40 and 40D. Importantly, the ground electrical connection 512 isto the ECA stripe 223 and the oxide-resistant sputter layer 165 and toferrule 122. This is the same as a system ground 144 electricalconnection 123 (3). In general, all of the filter components of thepresent invention are disposed on the device side of the hermetic sealinsulator ferrule to protect said components from body fluid.

FIG. 41 illustrates a ceramic body or insulator 188 that has been goldbrazed to ferrule 122. On the left-hand side of FIG. 41 , there is apeninsula structure, which is very similar to the ground peninsulastructure taught in FIGS. 13A, 13B and 13C. Instead of the leadwirestaught in FIGS. 13A, 13B and 13C, the peninsula provides a ground for aninternally grounded feedthrough capacitor 124′. The internally groundedfeedthrough capacitor ground electrode plates are connected to theleft-hand feedthrough capacitor via hole through electrical connection606 to the ECA stripe 223 and the oxide-resistant sputter layer 165 ofthe present invention. This provides the system ground 144 for theinternally grounded feedthrough capacitor. Internally groundedfeedthrough capacitors are taught by U.S. Pat. No. 5,905,627, thecontents of which are incorporated herein fully by reference. Referringnow again to FIG. 41 , one can see that the active via on the right-handside is a co-sintered conductive via consisting of conductive material602 and 604. In one embodiment, the end cap 602 is of substantially pureplatinum and the fill 604 is of CRMC. The conductive via can also havean oxide-resistant sputter layer 165 and an ECA stripe 223 forconvenient mounting of the internally grounded feedthrough capacitorthrough electrical connection material 606 and 606′.

FIG. 42 is very similar to FIG. 41 , except that the internally groundedfeedthrough capacitor is electrically attached to the ECA stripes usingan anisotropic conductive film 612. One can see that the ECA stripesstand proud of the insulator and the ferrule to aid in compressingconductive spheres 616. In the areas where the conductive spheres arenot compressed, they are not conductive 614. For simplicity, theoxide-resistant sputter layers 165 have been omitted from FIG. 42 .Referring back to FIG. 42 , one can see a nail headed structure isinserted or soldered or filled into the internally grounded feedthroughcapacitor 124′ via holes. Noble oxide-resistant sputter layer 164 alone,or in combination with the ECA stripe 223, is shown proud of a ferrule122 bottom surface. These proud areas compress the conductive particles616 of the ACF film 612. Therefore, electric conductivity only occurs inthese areas. In general, uncompressed ACF sphere 614 do not electricallyconnect or only electrically connect horizontally for a very shortspace. ACF films are ideal in the present application, as unlike moltensolder, they do not tend to dissolve the adjacent terminations. Thismakes the use of a relatively thick, but proud noble material 165(without the ECA stripe 223) an ideal and low-cost alternative.

FIG. 43 provides further detail regarding embodiments and materials thatcan be used in any of the embodiments of the present application.Included within this table are patents assigned to the present Applicantregarding EMI filter capacitor, EMI filter circuit boards, and hermeticco-sintered feedthroughs, all of which benefit from the low ESR lowinductance oxide-resistant attachment of the present application. Thecontents of the patents listed in this table are herein incorporatedfully by this reference.

What is claimed is:
 1. A feedthrough, comprising: a) a ferrule,comprising: i) a ferrule opening extending to a ferrule first sideopposite a ferrule second side; ii) a gold layer overlaying at least aportion of the ferrule second side; and iii) an electrically conductiveadhesive (ECA) overlaying and directly contacted to the gold layer; b)an insulator hermetically sealed to the ferrule in the ferrule opening,the insulator extending to an insulator first side at or adjacent to theferrule first side and an insulator second side at or adjacent to theferrule second side; c) at least one via hole extending through theinsulator to the insulator first and second sides; d) an electricallyconductive pathway disposed in and hermetically sealed to the insulatorin the at least one via hole; and e) a gold braze hermetically sealingthe insulator to the ferrule.
 2. The feedthrough of claim 1, wherein theferrule is of titanium.
 3. The feedthrough of claim 1, wherein theelectrically conductive adhesive (ECA) is selected from athermal-setting electrically conductive adhesive, an electricallyconductive polymer, an electrically conductive epoxy, an electricallyconductive silicone, an electrically conductive polyimide, athermal-setting electrically conductive polyimide, and mixtures thereof.4. The feedthrough of claim 1, further comprising a barrier layerselected from palladium, platinum and titanium-nitride directlycontacting at least a portion of the ferrule second side, and whereinthe gold layer directly contacts the barrier layer.
 5. The feedthroughof claim 1, wherein the gold layer has a thickness ranging from 10 nm to400 nm.
 6. The feedthrough of claim 1, wherein the electricallyconductive pathway hermetically sealed to the insulator in the at leastone via hole is selected from a lead conductor, a terminal pin, acircuit trace, and a platinum-containing sintered material.
 7. Afiltered feedthrough, comprising: a) a feedthrough, comprising: i) aferrule, comprising: A) a ferrule opening extending to a ferrule firstside opposite a ferrule second side; B) a gold layer overlaying at leasta portion of the ferrule second side; and C) an electrically conductiveadhesive (ECA) overlaying and directly contacted to the gold layer; ii)an insulator hermetically sealed to the ferrule in the ferrule opening,the insulator extending to an insulator first side at or adjacent to theferrule first side and an insulator second side at or adjacent to theferrule second side; iii) at least one via hole extending through theinsulator to the insulator first and second sides; iv) a terminal pindisposed in and hermetically sealed to the insulator in the at least onevia hole, wherein at least a second side portion of the terminal pinextends outwardly beyond the insulator second side; and v) a gold brazehermetically sealing the insulator to the ferrule; b) at least onecapacitor disposed on or adjacent to the ferrule and insulator secondsides, the capacitor comprising: i) a capacitor dielectric supporting atleast one active electrode plate and at least one ground electrode platein a spaced and interleaved relationship with each other; ii) at leastone active passageway extending through the capacitor dielectric,wherein a capacitor active metallization in the active passageway iselectrically connected to the at least one active electrode plate, andwherein the terminal pin second side portion extends into the capacitoractive passageway; and iii) a capacitor ground metallization attached tothe capacitor dielectric and electrically connected to the at least oneground electrode plate; c) an active electrical connection electricallyconnecting the terminal pin second side portion in the active passagewayto the capacitor active metallization electrically connected to the atleast one active electrode plate; and d) a ground electrical connectionelectrically connecting the capacitor ground metallization to the ECAdirectly contacting the gold layer overlaying at least a portion of theferrule device side.
 8. The filtered feedthrough of claim 7, wherein theferrule is of titanium.
 9. The filtered feedthrough of claim 7, whereinthe electrically conductive adhesive (ECA) is selected from athermal-setting electrically conductive adhesive, an electricallyconductive polymer, an electrically conductive epoxy, an electricallyconductive silicone, an electrically conductive polyimide, athermal-setting electrically conductive polyimide, and mixtures thereof.10. The filtered feedthrough of claim 7, further comprising a barrierlayer contacting at least a portion of the ferrule second side, andwherein the gold layer directly contacts the barrier layer.
 11. Thefiltered feedthrough of claim 10, wherein the barrier layer is selectedfrom palladium, platinum and titanium-nitride, nickel, rhodium,ruthenium, molybdenum, chromium, nickel-vanadium, nichrome, nickel-iron,palladium-cobalt, cobalt-tantalum, zirconium nitride, hafnium nitride,vanadium nitride, tantalum nitride, molybdenum nitride, tungstennitride, and mixtures thereof.
 12. The filtered feedthrough of claim 7,wherein the at least one capacitor is selected from a three-terminaldevice feedthrough capacitor, a multilayer ceramic chip capacitor, amonolithic ceramic capacitor, a flat-thru capacitor, and an X2Yattenuator.
 13. The filtered feedthrough of claim 7, further comprisingan insulative washer disposed between the insulator hermetically sealedto the ferrule and the at least one capacitor.
 14. A filteredfeedthrough that is configured for attachment to a housing for an activeimplantable medical device (AIMD), the filtered feedthrough comprising:a) a feedthrough, comprising: i) a ferrule, comprising: A) a ferruleopening extending to a ferrule body fluid side opposite a ferrule deviceside; B) a gold layer overlaying at least a portion of the ferruledevice side; and C) an electrically conductive adhesive (ECA) overlayingand directly contacting the gold layer; and ii) an insulatorhermetically sealed to the ferrule in the ferrule opening, the insulatorextending to an insulator body fluid side at or adjacent to the ferrulebody fluid side and an insulator device side at or adjacent to theferrule device side, wherein, when the ferrule hermetically sealed tothe insulator is attached to an opening in a housing of an AIMD, theferrule and insulator body fluid sides, and the ferrule and insulatordevice sides reside outside and inside the AIMD, respectively; iii) atleast one via hole extending through the insulator to the insulator bodyfluid and device sides; iv) a terminal pin disposed in and hermeticallysealed to the insulator in the at least one via hole, wherein at least adevice side portion of the terminal pin extends outwardly beyond theinsulator device side; and v) a gold braze hermetically sealing theinsulator to the ferrule; b) at least one capacitor disposed on oradjacent to the ferrule and insulator device sides, the capacitorcomprising: i) a capacitor dielectric supporting at least one activeelectrode plate and at least one ground electrode plate in a spaced andinterleaved relationship with each other; ii) at least one activepassageway extending through the capacitor dielectric, wherein acapacitor active metallization in the active passageway is electricallyconnected to the at least one active electrode plate, and wherein theterminal pin device side portion extends into the capacitor activepassageway; and iii) a capacitor ground metallization attached to thecapacitor dielectric and electrically connected to the at least oneground electrode plate; c) an active electrical connection electricallyconnecting the terminal pin device side portion in the active passagewayto the capacitor active metallization electrically connected to the atleast one active electrode plate; and d) a ground electrical connectionelectrically connecting the capacitor ground metallization to the ECAdirectly contacting the gold layer overlaying at least a portion of theferrule device side.
 15. The filtered feedthrough of claim 14, whereinthe ferrule is of titanium.
 16. The filtered feedthrough of claim 14,wherein the electrically conductive adhesive (ECA) is selected from athermal-setting electrically conductive adhesive, an electricallyconductive polymer, an electrically conductive epoxy, an electricallyconductive silicone, an electrically conductive polyimide, athermal-setting electrically conductive polyimide, and mixtures thereof.17. The filtered feedthrough of claim 14, further comprising a barrierlayer directly contacting at least a portion of the ferrule device side,and wherein the gold layer directly contacts the barrier layer.
 18. Thefiltered feedthrough of claim 7, wherein the barrier layer is selectedfrom palladium, platinum and titanium-nitride, nickel, rhodium,ruthenium, molybdenum, chromium, nickel-vanadium, nichrome, nickel-iron,palladium-cobalt, cobalt-tantalum, zirconium nitride, hafnium nitride,vanadium nitride, tantalum nitride, molybdenum nitride, tungstennitride, and mixtures thereof.
 19. The filtered feedthrough of claim 14,wherein the at least one capacitor is selected from a three-terminaldevice feedthrough capacitor, a multilayer ceramic chip capacitor, amonolithic ceramic capacitor, a flat-thru capacitor, and an X2Yattenuator.
 20. The filtered feedthrough of claim 14, further comprisingan insulative washer disposed between the insulator hermetically sealedto the ferrule and the at least one capacitor.